Who charges what
| O2 | Standard plans still include EU roaming under a fair-use ceiling — alone among the big four |
| Three & EE | Most newer plans charge daily fees in Europe; some older Three plans and higher EE tiers restore inclusive passes — the app confirms yours |
| Sky Mobile | Daily passes by band, switched in the app |
| All networks | Fair-use ceilings abroad; per-GB beyond; nothing unlimited past the border |
The pre-flight five
Spend cap on— free, in-app, the wall between a shock and a shrug.
Read your roaming screen— daily fee, pass or inclusive; and the ceiling number.
Longer than a few days?— price a local data eSIM against the daily fees; the pairing usually wins.
Kill background data— auto-backup and app updates off over mobile data.
Data OFF at sea— ferries and cruise ships bill via maritime satellite, which answers to no cap.
The dual-SIM pairing
Keep the UK line active for calls and texts; add a cheap local or regional data eSIM and route data through it. On any stay past a few days this routinely beats daily fees — full walk-through on the eSIM guide.