Best SIM-Only Deals UK 2026: Cut Your Mobile Phone Bill

The average UK pay-monthly mobile bill now sits at well over £20 a month once handset costs, mid-contract rises and extras are bundled in. Yet a quick look at the SIM-only market tells a different story: plenty of providers will give you a generous data allowance, unlimited calls and texts, and full 5G access for under £10 a month. If you already own a phone you are happy with, switching to a SIM-only plan is one of the easiest savings to bank.

The picture has also become friendlier for consumers since Ofcom’s April 2025 ruling banned percentage and inflation-linked mid-contract price rises on new contracts. Any annual increase must now be shown upfront in pounds and pence, so you can see exactly what you will be paying in year two before you sign up. Combined with the Vodafone-Three merger and aggressive MVNO competition, May 2026 is one of the best months in years to shop around.

Key Takeaways

• SIM-only plans from MVNOs like Smarty, giffgaff and 1pMobile typically beat the main networks on price for the same data allowance.
• Ofcom’s April 2025 rule banned CPI-linked mid-contract price rises; new contracts must show increases in pounds and pence (commonly £1.50 to £2.50 a year).
• 30-day rolling SIMs offer total flexibility and usually no annual price rise; 12-month deals are often a few pounds cheaper per month.
• Keep your number by texting PAC to 65075 — your network must reply with a code within a minute, and switching completes in one working day.
• MVNOs use the same masts as the main networks (Smarty/iD on Three, giffgaff/Tesco on O2, Voxi/Lebara on Vodafone, Lyca/1pMobile on EE) so coverage is broadly equivalent.

Why Now Is a Great Time to Switch

Three big factors have made SIM-only shopping much easier in 2026. First, Ofcom’s pounds-and-pence rule on mid-contract price rises (effective for new contracts from January 2025) has stripped away the inflation-plus-3.9% surprises that used to bite customers in their second year. Second, the Vodafone-Three merger completed on 31 May 2025 and the integrated VodafoneThree network has been pouring spectrum into the combined estate, lifting speeds on both brands. Three customers have seen average 4G speed bumps of around 20% as a result.

Third, MVNO competition is fiercer than ever. Smarty, giffgaff, iD Mobile, Voxi, Lebara, Tesco Mobile, Asda Mobile, Lyca and 1pMobile all run on the main networks’ masts but undercut their parent brands on price. The result is a market where £10 a month buys 60 to 100GB of 5G data on a 30-day rolling SIM — a deal that would have been unthinkable five years ago.

SIM-Only vs Phone Contract — Why SIM-Only Almost Always Wins

A two-year handset contract typically bundles the cost of the phone into your monthly bill at a markup, plus interest, plus annual price rises. Take a mid-range phone costing around £400 outright. Compare two indicative routes:

• Phone-on-contract: £28 a month for 24 months on 30GB data = £672 total. The handset element is roughly £17 a month (£408), the airtime element about £11.
• Buy phone outright + SIM-only: £400 phone + £9 a month SIM-only with 30GB = £616 total over the same 24 months — and you keep the phone with no further commitments after the SIM contract ends.

The SIM-only route saves around £56 in this example and leaves you free to drop your monthly cost further once the contract ends. The maths gets even better if you keep your existing phone or buy refurbished. Pay-monthly phone contracts only really make sense if you genuinely cannot fund the handset upfront — and even then, a 0% credit card or buy-now-pay-later option will usually beat the network’s interest.

Best SIM-Only Deals UK May 2026

Below are indicative SIM-only plans available across the three main data tiers. Prices are typical at the time of writing — always check the provider’s site for live offers, and bear in mind that introductory discounts often expire after 3, 6 or 12 months.

Light Users (5-10GB)

If you mostly use Wi-Fi at home and work and only need data for messaging, navigation and the occasional video clip, a 5-10GB plan is more than enough. 1pMobile and Lebara regularly run intro deals under £5 a month on this tier, with Smarty and iD Mobile close behind on no-frills 30-day rolling SIMs around £6-7.

Average Users (25-50GB)

This is the sweet spot for most UK households. Expect to pay around £8-12 a month for 25-50GB on a 30-day rolling SIM from Smarty, iD Mobile, Voxi or giffgaff. Tesco Mobile and Asda Mobile often match these prices on 12-month deals and throw in Clubcard or supermarket perks.

Heavy Users (Unlimited)

If you stream, tether or work on the move, unlimited data plans now start from around £15 a month at Smarty and iD Mobile. The main networks (EE, O2, Vodafone, Three) sit at £20-25 for unlimited, but tend to include extras like inclusive subscriptions, EU roaming and priority customer service.

30-Day Rolling vs 12-Month — Which Should You Pick?

A 30-day rolling SIM means you can cancel or change plan every month with no exit fee. It usually costs a pound or two more per month than the equivalent 12-month deal, but it gives you total flexibility — handy if your data needs are variable, if you might switch again soon, or if you want to dodge annual price rises (rolling SIMs from giffgaff, Smarty and 1pMobile typically do not raise prices mid-contract).

A 12-month contract locks in a lower headline price but ties you in for the full term. Under Ofcom’s April 2025 rule, any annual price rise must be stated in pounds and pence upfront — so you can see exactly what you will pay in month 13. For most households the saving is worth the commitment, but only if you intend to keep the plan for the full term.

How Mid-Contract Price Rises Work in 2026

Ofcom’s General Conditions were updated in 2024 and the changes took effect for new contracts from January 2025. The headline change: percentage-based and inflation-linked (CPI plus 3.9%) price rises are banned for new contracts. Networks must now state any annual increase in pounds and pence at the point of sale.

In practice, BT-owned providers (BT Mobile and EE) typically apply a £1.50 a month rise from 31 March each year for mobile customers. Vodafone, O2 and Three have adopted broadly similar approaches, with annual rises of around £1.50 to £2.50 a month depending on the plan. The flat-rate model hits cheap SIM-only plans proportionally harder — a £1.50 rise on a £6 plan is a 25% increase, while on a £20 plan it is just 7.5%.

If you want to avoid annual rises altogether, stick with 30-day rolling SIMs from MVNOs that have publicly committed to no in-contract increases — giffgaff, Smarty and 1pMobile are the obvious picks. Existing customers on contracts signed before January 2025 may still be on the old CPI-linked terms until their minimum term ends.

How to Switch Networks — PAC Code Process

Keeping your existing mobile number when you switch is free, fast and your legal right under Ofcom’s switching rules. Here is the process:

1. Text PAC to 65075 from the mobile number you want to keep. This works on every UK network.
2. Wait for the reply — your network must respond within a minute with your nine-character PAC code (three letters plus six numbers, e.g. ABC123456) and any early-exit fees you may owe.
3. Sign up with the new provider and give them your PAC code during the order process. It is valid for 30 days.
4. Choose your port date — the new provider will confirm when your number will move (usually the next working day).
5. Your old contract ends automatically on the porting date. You don’t need to call your old network to cancel.
6. Insert the new SIM (or activate the eSIM) on the port day. Your number transfers, your old SIM stops working, and you’re done.

If you don’t need to keep your number, you can request a STAC instead (text STAC to 75075) to cancel without porting.

Best Network for Coverage and 5G

Coverage tends to be the deciding factor once you have shortlisted on price. Opensignal’s January 2026 UK report ranks EE as the best all-round network, leading on 4G coverage, 5G availability and average download speed — EE now has 5G in 210+ towns and cities. O2 wins on overall coverage experience with around 99% 4G population coverage and 5G Standalone live in 500+ towns. Vodafone covers around 60% of the UK population with 5G and tends to be strongest on roads and in smaller towns thanks to its rural focus. Three (now part of VodafoneThree) has seen meaningful speed boosts post-merger and remains the value pick for data-hungry users.

For the best coverage in your specific area, always run a postcode check on each network’s online coverage map before you commit — the picture varies dramatically street by street.

Our Verdict — Best Pick for Most People

For most UK households, the sweet spot in May 2026 is a 30-day rolling SIM on Smarty or iD Mobile (both running on Three’s network) with around 30GB of data for £8 a month. You get 5G access, full UK coverage, no mid-contract price rises, and the freedom to switch again at any time. Light users should look at 1pMobile or Lebara for sub-£5 deals, while heavy users will find Smarty’s unlimited plan at around £15 hard to beat. If coverage in your area is poor on Three, switch to giffgaff (O2) or Voxi (Vodafone) — same MVNO value, different masts.

Frequently Asked Questions

How do I get a PAC code to switch?

Text the word PAC to 65075 from the mobile number you want to keep. Your network must reply within a minute with a nine-character code. The code is free, valid for 30 days, and works on every UK network.

Are MVNOs as good as main networks?

For coverage and speed in most situations, yes — MVNOs run on the main networks’ masts (Smarty and iD on Three, giffgaff and Tesco on O2, Voxi and Lebara on Vodafone, Lyca and 1pMobile on EE). The main differences are extras: MVNOs typically offer less generous EU roaming, fewer subscription perks, and shorter customer service hours. For the saving, most users find the trade-off easily worth it.

What is a 30-day rolling SIM?

A 30-day rolling SIM is a pay-monthly plan with no minimum term beyond the current month. You can cancel, upgrade or downgrade every 30 days with no exit fee. They typically cost a pound or two more than 12-month deals but offer full flexibility and usually no mid-contract price rises.

Will my plan price rise in 2026?

If you signed your contract from January 2025 onwards, any annual price rise must be stated in pounds and pence at the point of sale — typically £1.50 to £2.50 a month per year. Older contracts may still be on the old CPI-plus-3.9% terms until the minimum term ends. 30-day rolling SIMs from MVNOs like giffgaff, Smarty and 1pMobile generally do not raise prices.

Will my number transfer when I switch?

Yes — as long as you give your new provider a valid PAC code during sign-up. Your number transfers within one working day, your old contract ends automatically on that date, and there are no fees. You can keep using your phone normally while you wait.

Can I use my SIM in the EU?

Most UK SIM-only plans now include 5-25GB of EU roaming free of charge, either as standard or as a free add-on. Smarty includes 12GB, giffgaff 5GB, and Vodafone/Voxi/Lebara typically include their full UK allowance in the EU. EE, O2 and some others charge a small daily roaming fee (£2-3) on newer contracts — always check the terms before you travel.

Related Articles

• Best Cheap Broadband Deals UK April 2026
• Snoop UK Review 2026: Can a Free App Really Cut Your Bills?
• How to Save Money UK Beginners Guide: Smart Financial Tips for 2026
• How to Cut Your Energy Bills in 2026: A Complete UK Guide
• Best Money Saving Apps UK 2026: Plum vs Chip vs Moneybox vs Snoop