From January 2022, some UK mobile companies including EE and O2 will reintroduce roaming charges in Europe.
This is 6 months after most of the UK providors said they had no plans to do so after Brexit.
I post this, because it is quite common to see someone recommending picking up a UK SIM card to use on the continent (quite often GiffGaff is mentioned - who run their network on O2). BBC article is here