Know what your tariff actually covers

Roaming across Europe has become a bit of a patchwork since the UK left the EU. Some networks still bundle EU roaming into their plans, others charge a flat daily fee, and many apply a "fair use" limit — often around 25GB — before charging extra for data. Before you book anything, dig out your latest bill or log into your account and check three things: whether roaming is included, what your fair use cap is, and what a day of roaming costs if it isn't.

It is also worth knowing that receiving calls while you're abroad is not always free. On some tariffs, an incoming call can cost more than an outgoing one, so telling friends to catch you on a messaging app isn't just a nicety — it can be the difference between a few pounds and a nasty surprise.

Five minutes of settings before you travel

The simplest savings come from your phone's settings menu, and they take less time than making a cup of tea. Start here:

• Turn data roaming off at home. Switch it on only when you actually need it. Near the coast or close to a border, phones often latch onto a foreign network without you noticing.
• Set network selection to manual. Automatic mode can pick an expensive partner network. Choosing one manually gives you control and stops your phone hopping around.
• Turn off background app refresh and auto-updates. These quietly nibble at your data while your phone sits in your pocket.
• Disable Wi-Fi assist. That handy feature that tops up a weak Wi-Fi signal with mobile data is a roaming bill waiting to happen.
• Set a hard data cap in your phone's mobile data settings so you get a warning before things get silly.

Data: eSIMs, local SIMs and add-ons

For anything longer than a weekend, the cheapest data usually comes from a travel eSIM or a local prepaid SIM bought on arrival. An eSIM is the easiest option if your handset supports one: you buy a data bundle online before you go, install it, and keep your normal number active for calls and texts. Just remember to turn off mobile data on your home line, or you'll pay twice over.

A physical local SIM is still excellent value in many countries, though some require passport registration at the point of sale — so carry ID. Network add-ons are the least hassle and often the worst value, but they make sense for a two-day trip where convenience matters more than the price. Whichever you pick, do the heavy lifting — software updates, photo backups, streaming — on hotel Wi-Fi, and keep banking and anything sensitive off open public networks.

Calling and messaging without the shock

Voice calls over Wi-Fi or data cost you nothing beyond the data itself, so make the most of them. If you're on a data bundle or hotel Wi-Fi, a call through a messaging app is effectively free. Texts sent as SMS are chargeable abroad, and picture messages are worse — an MMS can cost a pound or more per image. Send photos through a data-based messaging app instead.

Two things catch people out. First, voicemail: dialling in to check messages while abroad is often charged at international rates, so if you're away for a while, consider switching voicemail off and telling people to message you. Second, long chats on a metered line add up fast. Keep mobile calls short, agree a time to talk on Wi-Fi, and don't be shy about asking people to call you back on a data app.

Habits that keep the meter still

Preparation beats penny-pinching every time. Download offline maps, playlists and any box sets before you leave, so you're not streaming on a foreign network. Save your boarding passes and tickets to your phone rather than relying on a signal at the gate. On ferries and in border regions, flick your phone into airplane mode — it will save battery and stop it connecting to a network you never chose.

Check your usage every couple of days through your network's app. It's far easier to rein in spending on day three than to argue about it on day ten. And if you're travelling with children, set their devices to Wi-Fi only before you hand them over — a cartoon marathon on mobile data is not a cheap way to pass a ferry crossing.

If something goes wrong

UK networks are required to apply a spending cap when you're roaming outside your inclusive allowance, unless you've agreed to raise it, and most will text you when you hit it. If a charge looks wrong, screenshot your usage and raise it with your provider as soon as you're home — complaints are handled far more smoothly with dates and figures to hand.

Finally, remember that a little planning goes a long way. Sort your settings, pick the right data option, lean on Wi-Fi where you can, and you can travel across Europe without giving your phone bill a second thought.