If you're going on a trip to London and don't want to land without data, an eSIM for London is the cleanest way to have internet as soon as you land: you install it before leaving home and it activates when connecting to British networks. In this guide, we'll get straight to the point: how many GB you need for a short trip, what the coverage is like on the Tube and at airports, and why Brexit changed the roaming rules.
Do I need an eSIM for London?
Yes, unless you're happy to rely on Wi-Fi in cafes and museums. An eSIM gives you your own data in London from the moment you land, with no queues to buy a physical SIM or bill surprises when you get back, and it works as soon as your phone connects to the British network.
In London, your phone is your constant co-pilot: you check Citymapper or Google Maps for the Tube, pay for transport, look for that recommended pub, or order a taxi. All of that eats data, and without a connection, you'll be stranded in the middle of Oxford Street. Public Wi-Fi exists, but it's patchy and requires registration. And if you're traveling from Spain, you no longer have the automatic European roaming that works in France or Italy. That's why it's most convenient to have your data sorted beforehand: you turn on your phone, activate the eSIM, and leave the terminal connected with the eSIM for the UK ready before you even fly.
Roaming after Brexit: what changed
Direct answer: Since Brexit, the UK is no longer part of European roaming. This means that your Spanish "roaming like at home" tariff does not cover you for free in London: many operators have started charging for data usage there again. A local eSIM bypasses this cost because it connects to British networks with its own tariff, not your Spanish operator's.
Before 2020, a Spaniard could use their data in London just like in Madrid thanks to the European "roam like at home" regulation. With the UK's departure from the EU, this protection no longer applies. Each Spanish operator now decides what to do: some keep the UK in their free zone, but many have removed it and apply tariffs that can be around €10-20 per day or a per-megabyte consumption that skyrockets. And they don't always clearly advertise it: you only find out when you receive the bill. Before traveling, it's advisable to check your specific situation; we tell you about it in this guide on roaming in the UK. If your operator charges, an eSIM compared to traditional roaming will be much cheaper and have a fixed price.
Tip: Don't assume that "Europe" includes the UK in your tariff. The UK, Switzerland, and Andorra are usually separate. Check the fine print of your plan before landing in London.
How many GB for 3, 4, or 5 days
For a long weekend, most travelers are comfortable with between 2 and 5 GB. The trick is how you use your phone: if you're using maps, WhatsApp, and social media, you'll use little; if you're streaming video, or sharing your connection with a laptop, it adds up quickly. In London, you'll have Wi-Fi in your hotel and many cafes, so download offline maps and series at night and save your data for when you're out and about. Here's a guide for normal use per day:
| Duration | Light use (maps, chat, social media) | Heavy use (video, hotspot, cloud photos) |
|---|---|---|
| 3 days | 1-2 GB | 3-5 GB |
| 4 days | 2-3 GB | 5-8 GB |
| 5 days | 3-4 GB | 8-10 GB |
| 1 week | 4-5 GB | 10 GB or unlimited |
If you're someone who uploads stories, makes video calls, or shares their connection with a tablet, aim for the higher end or directly for a generous data plan. If you're still unsure, we have a dedicated guide on how much data you need for travel with examples by traveler type so you don't overspend or run out.
Coverage in London: Tube, street, and neighborhoods
On the surface, London has excellent 4G and 5G coverage. Travel eSIMs connect to major British operators (EE, Vodafone UK, O2, Three), so you'll have plenty of signal in the city center, tourist areas, and residential areas. Around the London Eye, Camden, Notting Hill, or the City, you'll browse without problems, with speed for maps, streaming, and video calls.
The point to consider is the Underground (Tube). Deep tunnels historically had no signal, although Transport for London is rolling out 4G/5G coverage on more and more lines and platforms. Today, there's signal at many stations and sections, but don't assume you'll have data for the entire underground journey. The practical solution: download your route on Citymapper or Google's offline map before going underground, and reply to messages when you come to the surface. On double-decker buses, however, you're at street level, and coverage is continuous, so they're a great way to get around without losing connection. Outside London, if your plan covers the entire UK, you'll remain connected on your way to Windsor, Oxford, or even Scotland if you extend your trip.
Data at Heathrow, Gatwick, and other airports
The big advantage of an eSIM is that you arrive connected. As soon as your phone connects to the British network upon landing, you have data without looking for Wi-Fi or buying anything: you can order an Uber, check the train to the city center, or let people know you've arrived without any hassle. London has several airports, and each one reaches the center differently, so having data from minute one saves you trouble:
- Heathrow (LHR): the largest and closest. Metro (Piccadilly Line), Heathrow Express, or Elizabeth Line. With data, you can compare schedules and prices on the fly.
- Gatwick (LGW): to the south, connected by Gatwick Express and trains to the center. Useful for checking your ticket and platform from your phone.
- Stansted (STN) and Luton (LTN): those used by low-cost airlines. Further away, with buses and trains that should be booked on the go.
- London City (LCY): the most central, ideal if you're on business.
All of them offer free Wi-Fi, but it usually requires registration and doesn't cover you on the train or in a taxi. With the eSIM already activated, you don't have to worry: you leave the terminal browsing as if you were at home. Just make sure to activate data roaming in the eSIM line settings before taking off so it connects automatically upon arrival.
eSIM vs. hotel Wi-Fi and portable Wi-Fi
Many people think, "I'll just use the hotel Wi-Fi, and that's it." It works for the night, but it leaves you without a connection precisely when you need it most: on the street, on the Tube, looking for a restaurant or museum. London's public Wi-Fi exists, but it's slow, requires registration, and is unreliable for maps or payments. An eSIM gives you data with you at all times, not just when you're sitting in the lobby.
The other classic alternative is portable Wi-Fi (pocket Wi-Fi): a device you rent and carry with you. It works, but it has drawbacks compared to an eSIM: it's another gadget to carry, with its own battery that runs out, you have to pick it up and return it, and if someone moves away from the group, they lose connection. An eSIM is inside your phone, takes up no space, and there's nothing to return when you get back. For a short trip to London, portable Wi-Fi is unlikely to be worth it. If you want the details, compare eSIM vs. portable Wi-Fi.
How to activate your eSIM before flying
The best thing about an eSIM is that you can get everything ready from your sofa at home, using your Wi-Fi, without rushing. You buy the UK plan, receive a QR or a link, install it on your phone, and it's ready and waiting. The actual activation of the data happens automatically when you arrive in London and your phone picks up the British network; until then, you continue with your normal Spanish SIM.
The step-by-step process is simple:
- Check that your phone is eSIM compatible (almost all iPhones from the XS onwards and most recent mid-to-high-end Android phones are).
- Buy the UK eSIM before traveling and receive the QR by email.
- Install it from your phone's settings by scanning the QR, using your home Wi-Fi. Here's the step-by-step tutorial for installing an eSIM.
- Upon landing in London, select the eSIM as your data line and activate data roaming on that line.
- Done: you're browsing without touching your Spanish tariff. The whole process takes about 1 minute.
A tip: install the eSIM the night before your flight and give it a clear label ("London"). That way, when you arrive, you just have to select it and activate the data. If you're also traveling through continental Europe on the same trip, check out the 30-day Europe eSIM plans, although remember that the UK is usually separate, and a plan that includes it is advisable.
Frequently asked questions
Does eSIM work on the London Underground?
Yes, at many stations and sections, because Transport for London is rolling out mobile coverage across the network. But in some deep tunnels, there may still be no signal. The practical thing to do is to download your route on Citymapper or Google Maps before going underground and check messages when you come to the surface.
How many GB do I need for a 3-5 day trip to London?
With normal use of maps, messaging, and social media, between 2 and 5 GB is more than enough. If you do a lot of video, video calls, or share your connection, aim for 8-10 GB or a high data plan. At the hotel, you can use Wi-Fi and save your data for when you're out and about.
Can I use my Spanish tariff in London without paying more?
It depends on your operator. After Brexit, the UK left European roaming, so many tariffs no longer cover London for free and charge per day or per usage. Check your plan before traveling; if it charges, a local eSIM will be much cheaper and have a fixed price.
Do I have data as soon as I land at Heathrow or Gatwick?
Yes, as long as you have installed the eSIM before your flight and activated data roaming on that line. As soon as your phone connects to the British network upon landing, you're browsing without looking for Wi-Fi or buying anything at the airport.
Does the UK eSIM also cover Scotland and Wales?
Most UK plans cover the entire island: England, Scotland, Wales, and Northern Ireland. If your route includes Edinburgh or the Welsh countryside, check that the plan specifies "United Kingdom" in full and not just London or England.
Is my phone eSIM compatible?
Most recent phones are: iPhones from the XS onwards, current Google Pixels, and a large part of the mid-to-high-end range of Samsung, Xiaomi, or Motorola. You can check in your settings by looking for the option to add an eSIM or mobile plan, or by consulting the list of compatible models.
Conclusion
For a trip to London, an eSIM solves your connection without drama: you arrive browsing, avoid post-Brexit roaming, and only need 2-5 GB for a long weekend. Install it at home, activate it upon landing, and move around the City, the Tube, and the airports with data always at hand. Get your UK eSIM ready before you fly and land in London already connected, in just 1 minute.
