Cheapest UK Mobile SIM-Only Plans 2026: What You Actually Pay
We compared the real cost of UK SIM-only deals in 2026 after price hikes, loyalty discounts and one-month rolling contracts. Here is what you actually pay across the main networks and MVNOs.
Author
Maria Weber
Published on
Guide details and walkthrough
Why this guide exists
UK mobile plans changed shape in 2026 after Ofcom enforced new rules on mid-contract price hikes. Providers can no longer raise prices by "RPI plus 3.9 percent" without spelling out the exact pound increase at sign-up. The result: simpler comparisons, more rolling SIM competition, and several MVNOs undercutting the main networks in ways that did not exist 18 months ago.
This guide is based on live tariffs in May 2026, cross-checked against the public price tables on each provider site. Coverage assumes you have already checked the network's map for your post code.
The cheapest options by use case
If you barely use mobile data (under 5 GB)
Smarty 4 GB at 5 pounds per month rolling is the floor. Three network coverage. Rolling contract means you can change or cancel at any time. No mid-contract hike. Suitable for retired users, second SIMs, kids' phones, and anyone whose data live mostly on Wi-Fi.
1pMobile also competes here with a pay-as-you-go model that charges 1 penny per minute, text and MB, with a 10-pound annual minimum spend. Best fit for genuinely low-usage backups.
If you use 10 to 30 GB per month
Smarty 12 GB at 7 pounds per month rolling is the sweet spot. Data rollover on the Three network. No mid-contract hikes. The combination of price, flexibility and feature set is hard to beat for most users.
Voxi 25 GB at 12 pounds competes well if you want Vodafone coverage and Endless Tunes (uncapped music streaming that does not count against your data). Voxi is owned by Vodafone, so coverage matches the parent network.
Lebara 20 GB at 8 pounds rolling is interesting if you call international numbers - their international add-ons are the cheapest of the MVNOs.
If you want unlimited data
Voxi unlimited at 17 pounds rolling is the cheapest properly unlimited UK SIM in 2026. Vodafone network. No fair-use throttling above any threshold according to the current terms.
Smarty unlimited at 16 pounds rolling has been undercut by Voxi this year but adds data rollover even at the unlimited tier, which is unusual.
Three unlimited at 18 pounds on a 12-month deal is occasionally cheaper during promotions. Watch for the mid-contract hike disclosure - if it shows zero pound increase, it is genuinely cheaper than the rolling alternatives.
If you travel in Europe regularly
Lebara 20 GB at 8 pounds plus their 5-pound EU roaming add-on is the cheapest combined cost for typical EU travel patterns. No fair-use cliff that catches frequent travellers.
iD Mobile and Smarty both include free EU roaming up to a fair use cap (8 GB on Smarty, 22 GB on iD Mobile as of mid-2026). Check the specific cap before committing - it varies by tariff.
The full table
What we liked
- Rolling SIMs are now genuinely competitive with 12-month contracts on price
- Ofcom rules force clearer price-hike disclosure at sign-up
- MVNOs match the main networks on coverage in most areas
What could be better
- MVNO customer support is slower than EE, O2, Vodafone, Three direct
- Some perks only exist on parent-network contracts
- Coverage maps still need post-code-level checking
| Provider | Network | Best plan (mid-2026) | Monthly | Term |
|---|---|---|---|---|
| Smarty | Three | 12 GB | 7 pounds | Rolling |
| Voxi | Vodafone | Unlimited | 17 pounds | Rolling |
| Lebara | Vodafone | 20 GB | 8 pounds | Rolling |
| iD Mobile | Three | 30 GB | 9 pounds | Rolling |
| Tesco Mobile | O2 | 25 GB Clubcard | 9 pounds | 12-month |
| BT Mobile | EE | 25 GB BT customer | 10 pounds | 12-month |
| O2 | O2 | 20 GB | 14 pounds | 12-month |
| EE | EE | 25 GB | 18 pounds | 12-month |
The five questions to answer before switching
- What is your real monthly data usage? Check the last six months in your current provider's app. Most users overestimate. If your peak month was 8 GB, a 12 GB plan is the right tier.
- What coverage do you need where you actually live and work? Coverage maps are post-code specific. The bedroom signal and the office signal can differ wildly.
- Do you travel in the EU or further afield? Some MVNOs cap EU roaming aggressively. The main networks now charge extra for what used to be included.
- Do you call international numbers from the UK? Lebara and Lyca are far cheaper here than the main networks.
- How much do you value fast customer support vs price? This is the honest MVNO trade-off. Smarty support takes longer than EE support. The price gap is the compensation.
Switching the smart way
Save your PAC code by texting PAC to 65075 from your existing SIM. Order the new SIM, activate it, and submit the PAC within 30 days. Your old service stops the moment the new SIM activates with your old number. There is no overlap and no double billing.
Watch out for early termination fees on your existing contract. If you are mid-contract on a network that has not raised prices in line with the Ofcom rules, you may have a legal right to exit without fees - check the regulator's guidance and your contract terms.
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