Best SIM Only Deals UK — Keep Your Phone, Ditch the Contract
SIM only is the smart way to pay for your phone. Keep your handset, ditch the overpriced contract, and pay a tenner a month for more data than you'll use. We've compared the networks so you don't end up paying for signal you can't get or data you don't need.
Monthly Rolling vs 12-Month Contracts
Monthly rolling SIMs give you flexibility — you can cancel or switch with 30 days' notice. They're slightly more expensive per month than 12-month deals, but the freedom is worth it if you might change networks or if you're between handsets. If your phone is fine and you know where you'll be for a year, a 12-month deal is cheaper.
The best value in the UK right now is the 12-month SIM from the smaller networks — Smarty, iD Mobile, and Voxi regularly offer 30–100GB for £8–£12/month. That's less than a third of what the big networks charge for the same data on a phone contract. If you've paid off your handset or bought it outright, a SIM-only deal is the only sensible choice.
5G vs 4G — Is It Worth It Yet?
5G coverage in the UK is decent in cities and patchy everywhere else. If you live in a major city, 5G is worth having — download speeds of 200–500Mbps make a real difference for streaming and downloading. If you're in a town or rural area, 4G is still the reliable standard and 5G coverage is likely inconsistent.
Don't pay extra for 5G if you're not sure it's available in your area. Most SIM-only deals now include 5G at no extra cost on networks that support it. EE has the best 5G coverage, followed by Vodafone and O2. Three's 5G is improving but still trails. Check the network's coverage checker with your postcode before committing.
Data Rollover and Other Perks
Data rollover means unused data carries over to the next month. Smarty and Sky Mobile offer this — if you have a 30GB plan and use 15GB, the other 15GB rolls into the next month. Over a year, this can effectively double your usable data. It's the single most underrated feature in SIM-only deals.
Other perks to look for: EE includes free BT Sport (now TNT Sport) on some plans. Voxi includes unlimited social media data (WhatsApp, Instagram, etc. don't count against your allowance). iD Mobile includes roaming in 50+ countries. None of these should be your primary reason for choosing a network, but they're useful tiebreakers.
Network Coverage and eSIM Explained
Coverage is the most important factor. There are only four physical networks in the UK: EE, Vodafone, O2, and Three. Every other provider (Smarty, Giffgaff, iD Mobile, Voxi, Lebara, etc.) uses one of these four networks. EE has the best overall coverage and speed; O2 has the widest rural reach; Vodafone is solid; Three is budget but weaker in rural areas.
eSIM is a digital SIM that lets you activate a plan without a physical card. It's supported on iPhone 14+ and most recent Android flagships. It's useful for travel (add a local eSIM abroad) and for switching networks quickly. Most UK networks now support eSIM — check before signing up if your phone supports it. Rewild Mobile is a newer entrant worth considering for straightforward plans.
For most people, a 12-month SIM from Smarty, iD Mobile, or Voxi at £8–£12/month with 30–100GB is the sweet spot. Check coverage first — the best deal is useless without signal. Get data rollover if you can. And if your phone supports eSIM, it's worth having for the flexibility.