Published 14th October 2026
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Mobile data abroad is a small line in most holiday budgets and an unpredictable one. Providers set their own roaming charges, and the way the bill arrives depends on what your phone does in the background. This article sets out what Ofcom says UK providers must do, how to keep the cost known, and what to pack to keep a phone charged, including the airline rules for power banks.
What Ofcom says your provider must do
Ofcom's guidance for UK holidaymakers lists the protections that apply to roaming. When you enter another country, your provider must send you an automatic message explaining the roaming charges or usage limits, unless you have opted out. Providers must also publish their roaming charges on their website, and explain how to prevent accidental roaming near borders. Ofcom adds that your provider should be able to explain the relevant charges and any packages or discounts.
You can also set a monthly spend limit. Ofcom's page says that once you have set one, your mobile company must notify you when the limit is likely to be reached, and that your provider can only charge above the limit if you agree.
That gives a way to turn an open-ended cost into a number. Before you travel:
- Find your provider's roaming charges for the country you are visiting, on its website.
- Check whether it sells a daily or weekly bundle, which Ofcom suggests looking for.
- Set a monthly spend limit in your account or app, if you have not already.
- Enter the figure you expect to spend in your budget, with a margin.
The charges vary by provider and by plan, so use your own provider's published figure rather than a general average.
Ofcom's advice for keeping the bill down
The same page lists what travellers can do:
- Turn off data roaming.
- Use local Wi-Fi for maps, email and social media.
- Download playlists, podcasts and shows before you travel.
- Check whether children's devices could incur roaming charges.
- Avoid data-heavy activities such as streaming video or uploading photos.
- Consider a local SIM or an eSIM.
- Check costs with your provider before using your phone at sea, since ship satellite connections can cost more.
- Speak to your provider before travelling if you have an older phone, because 2G and 3G switch-offs abroad may affect service.
The ship point matters for anyone on a cruise or ferry, where Ofcom says satellite connections can cost more.
A local SIM means taking the UK SIM out for the trip, and a small Ad SIM card case with an eject pin keeps the original safe. An eSIM does not need a physical card, and the choice between the two depends on whether your phone supports it and what the provider charges. Ask your provider before you go, because that is the quickest way to find out.
Where it goes in the planner
The planner has fields for transport, accommodation and daily spending. There is no phone line, so fold the amount into days out, per person per day, or add it as a single figure to the total at the end. A bundle that covers a week for one price is easy to enter. An open-ended charge with a spend limit is entered at the limit.
Charging: the adapter
A phone that cannot be charged is a phone that cannot use its maps, its tickets or its boarding pass. Plugs differ by country, so buy a Ad travel adapter for the countries you are visiting and check its rating against what you are charging. A Ad multi-port USB charger means one adapter serves a phone, a watch and a power bank at the same time, which helps when there are fewer sockets than devices.
Short cables are also worth having. A Ad short USB charging cable is easier to manage in a hotel room where the socket sits behind the bed.
Power banks and the CAA rules
A power bank is the answer to a long day of maps and photos. The UK Civil Aviation Authority has set rules for carrying them, effective from 27 March 2026:
- Power banks must be carried in carry-on baggage, not checked luggage.
- Each passenger may bring up to two.
- They must not be recharged on board the aircraft, and the CAA says they should not be used to charge other devices on board.
- Lithium-ion power banks up to 100Wh are allowed without operator approval. Between 100Wh and 160Wh needs the operator's approval, and anything over 160Wh is not allowed in passenger baggage.
The CAA says always to check with your airline, because airline rules vary.
The CAA gives the sum if the rating is not printed on the battery: volts multiplied by amp-hours gives watt-hours, or volts multiplied by milliamp-hours divided by 1,000. A bank rated at 3.7V and 10,000mAh works out at 37Wh. Check the number on your own bank rather than assuming it, and choose a Ad power bank under 100Wh with the rating clearly printed on the case.
If the bag may go into the hold at the gate, take the power bank out first. The CAA's advice is to remove batteries and lithium devices from any cabin bag that will be taken to the hold at boarding. That is where a Ad small cable organiser pouch earns its place, because the whole charging kit comes out in one go.
Doing the sums before you travel
For a week away, the phone costs fall into three buckets: the data you buy, the charging kit you carry, and anything the phone does on its own that you did not plan for. The first is a figure from your provider's page. The second is one-off and mostly reusable on the next trip. The third is the one the spending limit exists to catch.
The hidden holiday costs article lists the other items that tend to be missing from a budget.