I was uncertain of the current situation in the main body of the UK,
but here, in Ireland if you live near the NI border your phone is
constantly hopping from one to another and you used to get stung
dreadfully for roaming costs. Having been subject to that as I drove
through the area, I've always made sure my phone is hard-set to my own
provider.

Several places around here (Folkestone) that I get the "Welcome to France"
text reminding me of my roaming costs... great reminder that I've forgotten
to turn it off :-)

I know a couple of people who have received calls while wandering around
Samphire Hoe and had a nasty surprise when the bill arrived!

Darren