All the UK Operators have full UK coverage, and most also offer coverage in all of Europe with the same SIM card.
Europe has a maximum mobile charge rate, so that a mobile operator can only charge up to the maximum so it doesn't matter really which UK network or European network you use the charges are about the same.
There are a couple of specific virtual operators that offer fairly cheap charges using the same SIM, the two I remember of the top of my head are Talk Mobile, offered by the UK's biggest mobile phone retailer, and Tesco Mobile from the UK's biggest supermarket
Bookmarks