Best SIM Only Deals UK 2026 — Top Monthly and 12 Month Plans

Quick Answer: Best SIM only deals in the UK for 2026 — Three’s unlimited plan at around £15/month for budget data, giffgaff’s no-contract goodybags for flexibility, and EE’s 12-month unlimited plans for the best network coverage. eSIM is now supported across all major UK networks, making switching faster than ever.

If you own an unlocked phone, a SIM only deal is almost always better value than a contract phone plan. You keep your handset, pay only for the service, and have far more flexibility to switch when a better deal emerges. In 2026, with 5G now widely available across all major UK networks and unlimited data plans starting below £15/month, SIM only has never offered better value.

Why This Matters in the UK in 2026

The UK mobile market is ferociously competitive. Four major networks — EE, Vodafone, O2, and Three — compete with dozens of virtual network operators (MVNOs) that lease capacity from them at wholesale rates and pass the savings on to consumers. The result is a huge range of choice at very different price points, all using the same underlying infrastructure.

Key developments in 2026:

5G is now mainstream across all four UK networks, with coverage extending well beyond the major cities into market towns and commuter belt areas. Ofcom’s February 2026 proposal to split the 6GHz spectrum for shared Wi-Fi and mobile use will further enhance capacity in dense urban areas.
eSIM support is universal across the major networks — you can switch providers and activate a new SIM digitally in minutes, without waiting for a physical SIM to arrive in the post.
The average UK mobile bill sits at £15–25/month, with genuinely unlimited data now available at the lower end of that range from Three and its MVNO Smarty.
12-month contracts typically save 20–30% compared to equivalent rolling monthly plans — significant if you know you want to stay on the same plan for a year.

SIM Only Deals Comparison April 2026

Network	Data	Price/month	Contract	5G	Best For
Three Unlimited	Unlimited	£15	Monthly	Yes	Cheapest unlimited
Smarty Unlimited	Unlimited	£16	Monthly	Yes	Transparent pricing
giffgaff 80GB	80GB	£12	Monthly goodybag	Yes	Flexibility, no contract
giffgaff Unlimited	Unlimited	£18	Monthly goodybag	Yes	O2 network, no contract
VOXI Unlimited	Unlimited	Yes (under 30s)	£13	Monthly	Young people
iD Mobile 100GB	100GB	£11	12 months	Yes	Budget 12-month
O2 Unlimited	Unlimited	£22	12 months	Yes	O2 ecosystem perks
Vodafone Unlimited	Unlimited	£23	12 months	Yes	Roaming, EU data
EE Unlimited	Unlimited	£25	12 months	Yes	Best UK coverage
EE Unlimited +	Unlimited	£30	12 months	Yes	Apple One/Roam Abroad

Prices as of April 2026. Introductory offers and cashback deals change frequently — check comparison sites for the latest.

The Four Major Networks — What Each Offers

EE — Best Coverage, Premium Price

EE consistently tops Ofcom’s network coverage and speed reports. Its 4G coverage reaches over 99% of the UK population and its 5G rollout is the most extensive of the four major networks. If you travel frequently across the UK — including rural areas, motorways, and less densely populated regions — EE is the most reliable choice.

EE’s SIM only plans come with useful extras: Apple TV+ or Amazon Prime Video are included with higher-tier plans, and its “Roam Abroad” feature allows data use in 48 destinations at no extra cost — invaluable for Europeans or frequent travellers to the US, Australia, or Canada.

The premium is real — EE’s unlimited plans start around £25/month compared to £15 on Three. For many users, particularly those in urban areas with strong coverage from all networks, that premium is hard to justify.

Best for: Frequent travellers across the UK, rural residents, anyone who values the very best coverage without compromise.

Three — Cheapest Unlimited Data

Three has built its reputation on value data, and in 2026 it maintains the most affordable unlimited data plans of the four major networks. Its 5G rollout has accelerated significantly and now covers most UK cities and large towns, though rural coverage still lags behind EE and Vodafone.

Three’s “Go Roam” feature historically allowed data use in 71 destinations — check current terms as these policies evolve. The network performs best in urban areas where Three has invested most heavily in infrastructure.

Best for: Heavy data users in cities, budget-conscious customers who prioritise data volume over coverage breadth.

O2 — Best Perks and Priority Access

O2 has differentiated itself through its Priority rewards programme — free coffees, early access to concert tickets, and discounts at major retailers including Greggs, Vue, and Nike. For O2 customers who make use of Priority, the perks meaningfully offset the slightly higher plan prices.

O2’s coverage is solid — second only to EE in most independent assessments — and its 5G rollout is progressing well. O2’s partnership with Tesco Mobile and giffgaff (both O2 MVNOs) means you can access O2’s network at significantly lower prices through those brands if you are willing to give up the Priority perks.

Best for: People who value loyalty rewards and regularly use O2 Priority discounts.

Vodafone — Best for Roaming and Business

Vodafone’s global network footprint makes it the strongest choice for frequent international travellers. Its EVO plans include data roaming in up to 83 destinations at no extra cost, and Vodafone has particularly strong business-focused extras including advanced cybersecurity features, Microsoft 365 bundles, and dedicated business customer support.

Best for: Frequent international travellers, business users, anyone who needs roaming across a wide range of countries.

MVNOs — Where the Real Value Hides

giffgaff — No-Contract Champion

giffgaff operates on the O2 network and has built one of the UK’s most loyal customer bases through its community model — customers help each other with technical queries through a forum rather than relying on traditional call centres, keeping costs low and passing savings to customers.

giffgaff’s “goodybags” are rolling monthly packages with no contract — you can change or cancel at the end of any month. This flexibility is unique among UK mobile providers at this price point. 80GB for £12/month and unlimited data for £18/month are both competitive with or better than any major network’s equivalent plans.

The O2 network underneath means solid UK coverage. The lack of a contract is a genuine advantage for people who like flexibility — travelling, testing plans, or waiting for a better deal to emerge.

Best for: Anyone who values no-contract flexibility, light to moderate data users, those already happy with O2 network coverage.

Smarty — Transparent Pricing Champion

Smarty, owned by Three, has built its brand on radical transparency. Its pricing structure is clear: you pay what is advertised, with no hidden fees, no mid-contract price rises (at the time of writing), and a unique data discount feature — if you use less data than your allowance, you get money back as a bill credit.

Smarty uses Three’s network, so 5G coverage in cities is solid. Monthly rolling plans are standard, and Smarty’s website clearly lists what you get with none of the small-print games that plague some mobile marketing.

Best for: Value-focused customers who dislike surprise charges, Three network coverage areas.

VOXI — Best for Under-30s

VOXI, Vodafone’s youth-oriented brand, offers a compelling deal specifically for customers under 30: unlimited social media data (WhatsApp, Instagram, TikTok, Snapchat) does not count against your data allowance. Rolling monthly plans with no contract, and prices from £13/month for a genuinely useful data package.

At 30, you age out of VOXI’s terms — at which point standard Vodafone or another network makes more sense.

Best for: Under-30s who use social media heavily and want no-contract flexibility.

iD Mobile — Best Budget 12-Month Deal

iD Mobile, owned by Currys and running on Three’s network, regularly offers the cheapest 12-month SIM only deals in the UK market. 100GB of data on a 12-month contract for around £11/month is a consistently competitive offer. iD also allows customers to roll over unused data to the following month — useful for variable usage patterns.

Best for: Budget shoppers willing to commit to 12 months for the cheapest per-month price.

Monthly Rolling vs 12-Month Contract — Which Should You Choose?

12-month contract advantages:

Typically 20–30% cheaper per month than equivalent rolling monthly plans
Price is locked in — no increases for 12 months
Most providers include additional data or perks on 12-month plans

Rolling monthly advantages:

Complete flexibility — cancel or change any month
No financial penalty if your circumstances change
Better if you are expecting a phone upgrade, a move abroad, or a major life change

The practical advice for 2026: If you know you will stay in the UK for the next year and are happy with your current phone, a 12-month deal represents meaningful savings. If you are uncertain about your situation or expect to get a new phone (potentially with a new contract), monthly rolling keeps your options open.

How to Switch Networks and Keep Your Number

Switching mobile providers is straightforward under UK regulations:

Get your PAC (Porting Authorisation Code): Text “PAC” to 65075 on your current number — your provider must give you the code within 1 minute by text and it is valid for 30 days.
Choose your new provider and sign up, providing your PAC during the process.
Your number transfers to the new network by end of the following working day — typically with just a few hours of service interruption.
eSIM switching: If both your old and new provider support eSIM, the transfer can happen digitally with no physical SIM needed and near-zero downtime.

You are not required to give notice to your old provider when using the PAC process — the new provider handles everything. Your old contract is automatically cancelled when the number ports.

Use our discount calculator to calculate the annual savings of choosing a 12-month SIM only plan over a rolling monthly equivalent.

Frequently Asked Questions

1. Which SIM only network has the best coverage in the UK? EE consistently achieves the highest scores in Ofcom’s independent coverage assessments — both 4G and 5G. For rural areas and motorway coverage in particular, EE’s network lead is significant. In urban areas, all four major networks perform comparably.

2. Is unlimited data actually unlimited on UK SIMs? Most “unlimited” plans include a fair use policy that throttles speeds above a very high threshold (typically 400GB–1TB/month) — thresholds that virtually no regular user reaches. In practice, unlimited plans in the UK deliver genuinely unrestricted data for normal use. Check the specific fair use policy before signing up if you use exceptionally large amounts of data.

3. What is the difference between 4G and 5G SIM plans? Most UK SIM plans include 5G access as standard in 2026 — you do not typically need a specific 5G plan. What matters is whether your handset supports 5G. Any 5G-capable phone will automatically use 5G where available regardless of which SIM plan you are on. In 4G-only areas, 5G phones seamlessly fall back to 4G.

4. Can I use a UK SIM in Europe after Brexit? Automatic free EU roaming ended after Brexit. Each network has its own roaming policy: Vodafone and EE include EU data roaming on their higher-tier plans; giffgaff, Three (with Go Roam), and O2 have varying policies. Always check your specific plan’s roaming terms before travelling to Europe to avoid unexpected charges.

5. What is an eSIM and should I get one? An eSIM is a digital SIM built into your phone — no physical SIM card needed. You activate it by downloading a profile digitally. All major UK networks now support eSIM, and all recent iPhones, Samsung Galaxy, and Google Pixel phones support eSIM. Benefits: instant activation, ability to have two numbers on one phone, no risk of losing a physical SIM.

6. Are MVNO networks reliable enough for everyday use? Yes. MVNOs like giffgaff (O2 network), Smarty (Three), and iD Mobile (Three) use exactly the same infrastructure as the parent networks — your calls and data travel over the identical masts and cables. The difference is in customer service responsiveness and extras like loyalty rewards, not network quality.

7. Which SIM only deal is best for heavy streamers? Any unlimited plan covers streaming without data anxiety. Three’s unlimited at £15/month is the cheapest entry point. For the best streaming speeds specifically in urban 5G areas, EE and Three deliver the highest consistent 5G throughput in independent tests.

8. How do I avoid mid-contract price rises? Ofcom rules permit providers to increase prices mid-contract if the terms are clearly stated at sign-up. Some providers (including Smarty, at time of writing) offer genuinely fixed-price contracts. For major networks, 12-month contracts limit exposure to one potential annual increase. Check the specific price rise terms in your contract before signing.

9. Can I have two SIMs on one phone? Most modern smartphones support dual SIM — either two physical SIM trays or one physical SIM plus eSIM. This is useful for keeping work and personal numbers separate on one device, or maintaining UK service while using a local data SIM abroad.

10. What happens to my giffgaff goodybag if I do not renew it? Your giffgaff number stays active for up to 6 months without a goodybag — you can still receive calls and texts but cannot make calls or use data. If you do not activate a goodybag or make a chargeable activity within 6 months, your number is recycled. For infrequently used numbers, a £10 goodybag every few months keeps the number active affordably.