The UK has four major networks - EE, O2, Vodafone, and Three - with good 4G coverage in all major cities and towns. Coverage in rural areas is a known weak spot compared to, say, Germany or South Korea, but for typical tourist routes it's consistently fine.
Coverage overview
London: full 4G everywhere. EE and O2 have good coverage on the Tube now - the Elizabeth line is fully covered, the older deep-level lines have improved significantly. Surface lines have good signal throughout.
Manchester, Birmingham, Edinburgh, Glasgow, Bristol, Leeds - all well-covered in city centres and suburbs. Signal holds up on main motorways (M1, M6, M25 etc.) consistently.
The Scottish Highlands are the UK's most significant coverage gap. Rural areas around Inverness, the Northwest Highlands, the Outer Hebrides, and parts of the Isle of Skye can be genuinely sparse. EE has the best rural UK coverage overall - if you're doing a Highland road trip, EE-backed plans are the right choice.
Wales - Cardiff and main towns are fine. Rural mid-Wales and some of the national park areas (Brecon Beacons, Snowdonia) have gaps. The coastal paths are variable.
5G in the UK
London, Manchester, Birmingham, Edinburgh, and major cities have widespread 5G from all four carriers. EE has arguably the most mature 5G network. Outside major cities, 5G coverage thins significantly - don't rely on it outside urban areas.
For international visitors
If you're visiting from within Europe, your EU roaming plan from home may work in the UK - check whether post-Brexit your carrier still includes UK coverage (many do). For non-European visitors, a UK eSIM plan is the obvious choice.
Three UK is historically the most generous with international roaming for UK residents, which is less relevant for visitors. For incoming tourists, the carrier used by the eSIM plan matters less in cities but matters more in rural areas - EE-backed coverage is best for anywhere outside the cities.
London with data
London is a city where data earns its keep. The Tube network is enormous (270+ stations) and confusing the first few times. Google Maps and Citymapper both handle Tube routing well, showing you which line to take, where to change, and which exit to use at the other end. Citymapper is particularly good for London - it's a local app that factors in real-time delays and even tells you which carriage to stand in for the quickest exit at your destination.
Contactless payment works on all London transport (buses, Tube, Overground, DLR, and most National Rail within London). Your phone's contactless via Apple Pay or Google Pay works too. Having data means your phone doubles as your transport card - no need to buy an Oyster card if your phone's working.
Black cabs are expensive. Uber is cheaper and widely available. The bus network is excellent and very cheap (1.75 pounds per journey, capped at 4.65 pounds per day). Having data to check bus routes on Google Maps or TfL Go makes the bus system much more accessible to visitors.
Scotland road trip tips
The classic Scotland road trip - Edinburgh up through the Highlands to Skye and back - is genuinely stunning. But the connectivity situation is genuinely patchy in the Highlands. Download the full Scotland offline map in Google Maps before leaving Edinburgh. Fort William and Inverness have solid coverage and are good places to download content and sync anything you need.
The Isle of Skye has coverage in Portree and the main village areas. The Fairy Pools, Old Man of Storr, and Quiraing hike have intermittent signal at best. The A87 road to Skye over the bridge has coverage, but the single-track roads to remote areas of the island drop off.
Beyond London: popular tourist areas
The Cotswolds (Bourton-on-the-Water, Bibury, Stow-on-the-Wold) have decent coverage in the villages. The driving routes between them are mostly covered. Bath is fully covered and compact enough to walk around easily with Maps. Stonehenge has signal (it's a flat plain in Wiltshire with good infrastructure). The Lake District has solid coverage in Windermere, Ambleside, and Keswick. Higher fells and remote valleys can lose signal - check conditions before heading up Helvellyn or Scafell Pike.
Oxford and Cambridge are both small, well-covered university cities where data is useful mainly for finding the right college entrance (they all look the same from outside) and locating the good pubs, which are tucked away on back streets.
How much data?
London is excellent for Maps, public transport apps (TfL Go is the Transport for London app and is very good), and all the usual connectivity needs. A week in London: 3-5GB is fine. UK road trip including rural areas: 5-8GB with offline maps downloaded. Two weeks covering London plus Scotland: 8-10GB gives you comfortable headroom for everything. Check /esim-in-united-kingdom on getesimonline.com for plan options.