I will get a new iPhone in the UK. I'm hoping - like in the US - any provider serves the whole UK - England, Wales, Scotland, Ireland.

Then, I'm hoping there is a provider that might serve European countries, even if that means swapping SIM cards, from country to country, to fit local cell phone frequencies.

I'm still trying to educate myself about this. When I was in Poland in 2009, the price of an iPhone was like $900US, and that didn't fit my plans. I did have the use of a low cost non-smart phone, but really didn't use it because for me it was 2000 era technology. I left my AT+T iPhone off, except for sending 3 text messages pertaining to travel plans.