There are five 3G UK networks: Vodafone, O2, Three, Orange, and T-Mobile. They will have coverage checkers on their websites, but some of them you will need the

There are five 3G UK networks: Vodafone, O2, Three, Orange, and T-Mobile. They will have coverage checkers on their websites, but some of them you will need the postcode of the address you're staying at to use. (Note: you mean Romford, probably the one in North East London (near Havering).)