Mobile Carriers in the United Kingdom

The UK has four mobile networks. Everything else you can buy — and there are dozens of brands — runs on one of those four. Get that straight and the whole market stops looking like a maze.

The four are EE, O2, Vodafone, and Three. EE, owned by BT, has the widest 4G and 5G reach and usually tops the independent coverage tests. O2 has strong city coverage and a loyal base. Vodafone and Three agreed to merge, and the combined network is now rolling out under the Three/Vodafone umbrella — if you're on either, expect coverage to keep shifting in your favour over the next couple of years.

Here's the part that saves people money. Most cheap SIM-only deals come from MVNOs — resellers that buy capacity wholesale and sell it under their own name. Giffgaff and Voxi run on O2 and Vodafone respectively. Smarty runs on Three. Tesco Mobile and Lebara also sit on O2. The network underneath is identical to the big-brand version, so the only real question is which host network covers your area best.

Which network actually covers you

Coverage is local, not national. EE wins most published league tables, but I've watched Three beat it flat in central London and lose badly in a Welsh valley twenty miles on. Before you commit, check the operator's own coverage map for your postcode and the places you spend time — home, work, the commute between. A network that's brilliant at your desk and dead at your front door is useless.

If you can't decide, EE is the safe default for rural and travel-heavy use, and an O2 or Three MVNO is the value pick if their map looks solid where you live.

MVNOs: same signal, smaller bill

The trade-off with an MVNO isn't worse coverage — it's the same masts — it's usually data priority during congestion and fewer perks. Giffgaff has no contracts and a famously good community forum for support. Smarty bills only for what you use and refunds unused data. Tesco Mobile throws in Clubcard points. None of them will hand you free Disney+ or stadium presale tickets the way the big four sometimes do, and for a lot of people that's a fair swap for halving the bill.

eSIM and switching

All four networks support eSIM on modern phones, and most of the larger MVNOs now do too. Switching is genuinely easy here: text the word PAC to 65075 and your current provider must send a switching code within a minute, then your new SIM goes live the next working day with your number intact. Ofcom forced that one-text process through precisely because porting used to be a nightmare.

Each carrier page below lists verified APN settings, MMS values, and eSIM steps. If your data stopped working after a SIM swap, the APN is almost always the culprit — start there.