Best SIM Only Deals UK 2026

Finding the best SIM only deals UK 2026 comes down to two things right now: how much data you actually use, and whether your network is going to quietly raise your bill every April. The big four — EE, O2, Vodafone and Three — have all moved to fixed pounds-and-pence annual price rises since Ofcom banned inflation-linked increases on contracts taken out from 17 January 2025. EE adds £1.50 a month each year, O2 and Vodafone add £2.50, and Three adds between £1.80 and £2.30 depending on your data allowance. A growing list of MVNOs — SMARTY, iD Mobile, Lebara, giffgaff, VOXI, Honest Mobile and 1pMobile — have committed to no annual rise at all. This guide covers the best deals across every category — budget, unlimited, longer contracts and international calls — with September 2026 prices and a clear note on which networks won’t touch your bill mid-contract.

If you’re weighing up whether switching makes sense for you, our guide to SIM-only vs phone contract has the full breakdown. The short version: buying a phone SIM-free and pairing it with a cheap SIM can save you roughly £185 to £280 over two years — around £8 to £12 a month — compared with a typical ~£42/mo handset contract (based on iPhone 16 pricing, checked September 2026). Once your old handset contract ends, that gap only widens, because the contract keeps charging £40 or more a month for a phone you already own.

Last updated: 6 September 2026 — prices re-checked across all networks.

Our top picks: best SIM only deals in September 2026

The best all-round SIM deal right now is iD Mobile’s 110GB plan at ~£10/mo (as of September 2026), because it pairs a huge data allowance with a firm no-annual-price-rise pledge. Here’s a quick at-a-glance comparison of the deals we cover in this guide. Prices were checked in September 2026 and are marked with ~ where they represent introductory or approximate rates.

Quick verdict cards

Best SIM only deals under £10 a month

You don’t need to spend much to get a decent SIM. Under £10/mo you can currently get 30GB on Three’s network for ~£7/mo (iD Mobile), 40GB on Vodafone’s for ~£7.95/mo (Talkmobile), or a Lebara promo that starts at ~£3.18/mo — all checked September 2026. Here are the standouts.

Lebara — from ~£3.18/mo (promo)

Lebara runs one of the cheapest introductory offers on the market. Through comparison channels you pay ~£3.18/mo for the first three months, then it steps up to ~£7.95/mo on a 30-day rolling basis (checked September 2026, via Uswitch). The exact data allowance on that promo tier isn’t shown in the listing, so check it when you click through. Buying direct from Lebara, 5GB is ~£5/mo and 30GB is ~£10/mo (as of September 2026), both on Vodafone’s network. Every Lebara plan also includes international minutes, there’s no credit check, and Lebara has not raised its prices since 2020.

The main thing to watch: Lebara’s coverage is only as good as Vodafone’s in your area, so check the Vodafone coverage map before switching. The introductory price also runs out after three months — set a calendar reminder, and because it’s 30-day rolling you can switch again without penalty if ~£7.95/mo doesn’t suit you.

SMARTY 40GB — ~£10/mo

SMARTY is owned by Three and runs on Three’s network, which has the fastest average 5G speeds in the UK. At ~£10/mo for 40GB on a 30-day rolling plan (as of September 2026), it’s a clean value pick, and SMARTY often runs special offers that bump a tier’s data — the 100GB plan is currently giving 140GB for ~£12/mo. Smaller plans sit at ~£9/mo for 20GB, ~£8/mo for the 16GB tier (currently 32GB on offer), and ~£6/mo for 5GB. No price rises, no long-term commitment, and 5G is included at no extra charge.

SMARTY doesn’t roam in as many destinations as some rivals, so check the list if you travel often. But for a pure UK everyday SIM with solid coverage and no bill shock, it’s hard to beat. There’s also a refer-a-friend credit scheme that can cut your monthly cost further.

iD Mobile 30GB — ~£7/mo

iD Mobile is another Three MVNO with a strong reputation for flexible, low-cost plans. The 30GB plan at ~£7/mo (as of September 2026) is a 1-month rolling deal, so there’s no long commitment. There’s also 20GB for ~£6/mo and 40GB for ~£8/mo. iD Mobile’s stand-out feature is data rollover: anything you don’t use in a month carries forward to the next, so you’re not throwing away what you’ve paid for. EU roaming is included, and iD has committed to no annual price rise.

Two more sub-£10 options worth a look, both on EE’s network with a no-price-rise pledge: Honest Mobile’s 40GB plan at ~£6.95/mo (a fixed-price promo, as of September 2026), and 1pMobile at ~£6/mo for 4GB or ~£7.50/mo for 5GB. Talkmobile’s 60GB plan on Vodafone’s network is ~£7.95/mo on 30-day rolling.

Best unlimited data SIM only deals

The cheapest genuine unlimited-data SIM right now is giffgaff at ~£14/mo on an 18-month plan (limited-time, standard ~£25/mo), with iD Mobile’s ~£15/mo plan the cheapest without a promo catch — both checked September 2026. “Unlimited” doesn’t always mean the same thing between networks, though. For the fine print on throttling and fair-use policies, our guide to the best SIM deals for heavy data users goes deeper.

giffgaff Unlimited — ~£14/mo (18-month)

giffgaff’s unlimited plan is ~£14/mo on an 18-month term as a limited-time offer (standard price ~£25/mo, as of September 2026). It runs on O2’s network, there’s no credit check, and giffgaff operates a price lock — no mid-contract rises, so £14 holds for the term. There’s also a rolling monthly unlimited plan at ~£20/mo (limited-time; standard ~£35/mo) if you don’t want the 18-month commitment.

The catch is the 18-month tie-in and the fact that this is promotional pricing — if you sign up after the offer ends, you’re closer to £25/mo. Check the live price before you commit, and factor in that O2’s network is average rather than class-leading for 5G speed.

iD Mobile Unlimited — ~£15/mo (24-month)

For unlimited data at a standard price with no promo expiry to track, iD Mobile at ~£15/mo on a 24-month contract (as of September 2026) is the strongest pick. You’re on Three’s network — the fastest average 5G in the UK — with no fair-use throttling for personal use, unlimited calls and texts, and iD’s no-annual-price-rise pledge, so £15 holds for the full two years. Via MoneySavingExpert the same plan sometimes comes with a gift card that brings the effective cost down to around ~£12/mo across the term.

This is the MVNO route to true unlimited: the same Three signal as a direct Three contract, usually cheaper, and with the price fixed. The trade-off is that priority can sit with direct Three customers during network congestion, though that’s rarely noticeable in practice.

SMARTY Unlimited — ~£20/mo (30-day rolling)

SMARTY’s unlimited plan is ~£20/mo on a 30-day rolling basis (as of September 2026) — more than giffgaff’s promo or iD’s standard rate, but you’re not tied in for a single month and there are no price rises. On Three’s network, that’s a lot of flexibility for the money. Three’s own 12-month unlimited plan is also ~£20/mo (rising to around £22.30 from April 2027), and Asda Mobile does unlimited on Vodafone’s network for ~£19/mo on a 24-month deal with no price rise.

EE Unlimited — ~£31.50/mo

EE is consistently rated one of the UK’s best networks for coverage, particularly in rural areas. Its unlimited data plan on a 30-day basis is around ~£31.50/mo (as of September 2026), though note that entry-level EE unlimited plans cap speeds at 25Mbps — you pay more for uncapped 5G. EE’s coverage map is broader than Three’s across many rural postcodes, so it’s the better choice if you live or work outside cities. EE’s pay-monthly SIM contracts also carry a fixed £1.50/mo annual rise each 31 March; its 30-day and pay-as-you-go plans do not.

Best 12-month SIM only contracts

A longer contract commits you for a year or two but usually rewards that with a lower monthly price. Three’s 12-month plans start at ~£7/mo for 30GB and ~£8/mo for 60GB (as of September 2026); iD Mobile’s biggest-data plans need a 24-month term but drop to ~£10/mo for 110GB. The deals below are the ones worth the tie-in.

Three 60GB — ~£8/mo (12-month)

Three’s 60GB plan at ~£8/mo on a 12-month contract (as of September 2026) is the pick if you want a direct relationship with a big-four network rather than an MVNO. The 30GB plan is ~£7/mo, 80GB is ~£10/mo and 120GB is ~£12/mo. Three has the fastest average 5G in the UK and no fair-use throttling on unlimited. The catch is the annual rise: Three adds a fixed £1.90/mo each April on plans between 5GB and 99GB, and £2.30/mo on 100GB-plus plans — so budget for one increase during a 12-month term and two over 24 months.

iD Mobile 110GB — ~£10/mo (24-month)

This is the best value large-data SIM available in September 2026. iD Mobile’s 110GB plan is ~£10/mo on a 24-month contract, with 175GB at ~£12/mo. You get Three’s network, data rollover, and iD’s no-annual-price-rise pledge — so unlike a Three contract, the price you sign up at is the price you pay for the full two years. If you’re after a set-and-forget plan with more data than you’ll realistically use, this is it. The only real downside is the 24-month tie-in, so be confident Three’s coverage is good where you live.

Talkmobile 100GB — ~£4.98/mo for 3 months, then ~£9.95/mo

Talkmobile’s 100GB 12-month plan runs at ~£4.98/mo for the first three months, then ~£9.95/mo for the rest of the term (as of September 2026). It runs on Vodafone’s network, and there’s a 150GB tier at ~£5.97/mo then ~£11.95/mo. Talkmobile markets itself on budget pricing; we could not independently confirm whether it applies a separate annual in-contract rise on top of the promo step-up, so check the terms before you sign.

O2 100GB Plus — £19.99/mo (24-month)

O2’s 100GB Plus plan is £19.99/mo on a 24-month contract as an offer running to 30 September 2026 (as of September 2026), after which it reverts to standard pricing. Every O2 plan includes unlimited calls and texts plus O2 Priority — a perks scheme with regular freebies, presale tickets and retailer discounts. The catch: O2 applies a fixed £2.50/mo annual rise each April, so expect it to reach around £22.49/mo from April 2027 and ~£24.99/mo from April 2028.

Best SIM only deals for international calls

If you regularly call abroad, a standard SIM plan can quietly rack up big bills. Lebara is the standout, with calls to 50+ countries included as standard from ~£5/mo (as of September 2026). Lycamobile is the other name built around international calling, though we could not reconfirm its pricing for this update.

Lebara — from ~£5/mo, calls to 50+ countries

Lebara includes calls to 50+ countries in all its plans — not as an add-on, but as standard. Its 5GB plan is ~£5/mo on a 30-day rolling basis with no credit check (as of September 2026), and the promotional deal via comparison sites starts at ~£3.18/mo for three months before stepping up to ~£7.95/mo. EU roaming is free and India roaming is free too — the latter making it particularly popular with the UK’s large South Asian community. Lebara runs on Vodafone’s network, so UK coverage is strong, and it hasn’t raised prices since 2020.

If you use data heavily, the 50GB plan at ~£15/mo bought direct is the better fit, but the 5GB entry plan is remarkable value if your main use is international calls with some data on the side. There’s no contract, so you can move if a better deal comes along.

Lycamobile — calls to 70+ countries

Lycamobile takes the international angle further, with minutes to 70+ countries included across its plans, EU roaming included, and eSIM support. Entry plans have historically started from around £2.50/mo on promotional rates, then risen to roughly £5/mo — but we were not able to reconfirm Lycamobile’s pricing for this September 2026 update, so treat those figures as indicative and check the live price before ordering.

Lycamobile’s app and customer service reviews are mixed. The plans are good value, but if you hit a problem, resolution can take longer than with a direct network. For straightforward use — international calls plus some data — it’s a reasonable pick; for anything complex, factor in the support experience.

Price rises: which networks won’t hike your bill?

The big four all still raise prices mid-contract — they’ve just changed how. Ofcom banned inflation-linked (CPI or RPI plus a few percent) mid-contract rises on any contract taken out from 17 January 2025. Since then, EE, O2, Vodafone and Three have all switched to fixed pounds-and-pence annual increases that must be shown upfront at sign-up. That’s more predictable than the old system, but it’s still a rise every year — and a fixed £2.50/mo adds up faster on a cheap plan than an old percentage would have.

Here’s the current picture for the main networks (as of September 2026):

The confirmed no-rise networks — SMARTY, iD Mobile, Lebara, giffgaff, VOXI, Honest Mobile and 1pMobile — are all MVNOs. That’s not a coincidence. MVNOs compete on price, so building in annual rises would undercut the reason people choose them. Talkmobile advertises budget pricing but its promo 12-month plans step up from the introductory rate to the standard rate after three months, which is a promo expiry rather than an inflation rise; we couldn’t independently confirm whether it also applies a separate annual increase, so check before signing.

The practical maths: take a big-four 100GB plan at ~£20/mo on a 24-month contract. Three adds £2.30/mo each April, O2 and Vodafone £2.50/mo — so by the second year you’re paying ~£22.50/mo, and more if you keep it longer. An MVNO like iD Mobile at ~£10/mo for 110GB, or SMARTY at ~£12/mo for 140GB, never moves. The MVNO is cheaper on day one and the gap only widens.

MVNO vs main network: same signal, lower bill?

An MVNO (Mobile Virtual Network Operator) is a company that buys wholesale access to one of the big four networks — EE, O2, Three or Vodafone — and resells it under its own brand. You get the same signal towers. The differences are the pricing, the customer service setup, and any extras the MVNO adds or removes.

Here’s which MVNO runs on which parent network (as of September 2026):

The question most people ask: will I notice the difference between an MVNO and the parent network? In day-to-day use, almost never. The signal, speed and 5G access are identical — you’re on the same masts. Where you might notice something is during peak congestion, when some networks give priority to their own-brand customers over MVNO traffic. In practice that rarely affects performance noticeably. Customer service is the more real difference — direct network customers generally get faster resolution for account issues.

For most people comparing value, an MVNO on the right parent network is the smarter choice. The savings are real, the signal is the same, and the no-price-rise guarantee from most MVNOs is increasingly hard to ignore as the big four keep hiking every April. If you also want to compare phone contracts alongside SIM-only, that comparison is worth doing before you commit.

How to switch to SIM-only and keep your number

Switching networks is straightforward. The whole process can be done in under 10 minutes if you know the steps. Here’s how to do it without losing your current number.

1. Get a PAC code from your current network. Text “PAC” to 65075 — your current provider must reply within 60 seconds with your Porting Authorisation Code. This is a free text, and the PAC is valid for 30 days.
2. Choose your new SIM deal. Use the comparison table at the top of this guide to pick your preferred plan. Make sure the network has good coverage in your area — check the provider’s coverage map using your postcode.
3. Order your new SIM. Sign up online and select “I want to keep my number.” You’ll need to enter your PAC code during the sign-up process. The SIM typically arrives within 1–3 working days.
4. Wait for the switch to happen. Your number transfers to the new network on the date you agreed during sign-up. It usually happens overnight. You may lose signal for a few hours during the switch.
5. Insert your new SIM and check it’s working. Make a test call and check your data connection. If everything’s working, you’re done. If not, contact your new network’s customer service — they have 24 hours to resolve porting issues.
6. Cancel your old contract if needed. If you were on a rolling plan, it cancels automatically when you port out. If you’re on a fixed contract, check your end date — leaving early may trigger an early-exit fee.

If you’re bundling your mobile plan with a new broadband package, it’s worth comparing providers on both fronts — our TalkTalk vs Virgin Media broadband comparison covers one of the more common match-ups.

Frequently asked questions about SIM only deals UK

Closing disclosure: TheTechVector earns a commission if you sign up via affiliate links on this page, at no extra cost to you. The Lebara, O2 and EE Mobile links are tracked affiliate links; iD Mobile, SMARTY, giffgaff, VOXI, Three and Talkmobile are covered editorially with no affiliate link. All prices were checked in September 2026 and are subject to change. Always verify the current price at the provider’s website before signing up.

Written by Vaibhav Kulkarni

Vaibhav is the founder and technical editor of TheTechVector, with 15 years’ experience in quality engineering and software testing. He applies that background to auditing spec sheets, comparing price-to-performance, and checking hardware compatibility across our UK broadband, laptop, VPN, and smart home guides. All prices are checked before publication — if something’s out of date, let us know.