@Sandee626
sorry, PM does NOT have roaming services in UK. In fact, PM only has roaming in US and Mexico and nowhere else
For data while you traveling, you will have to use local data sim or travel eSIM such as Airalo.
For voice calls and SMS from friends, you can download VoIP app TextNow and use the app for that. Make sure you setup TextNow before your trip. You can even forward voice calls to the number provided by TextNow right before you leave Canada
For RCS and iMessage, you can still send receive them with local data or Wifi. But remember to enable PM sim and turn on Roaming for iMessage and RCS to work (the actual roaming services won't work, but enabling the sim and roaming allows iMessage/RCS to validate your phone number)
But if you are expecting 2FA from banks/email/businesses , you won't receive them while you travel without roaming. You will need to arrange to change to receive via email or app ahead of your trip
