3G cell service in London UK

Just a quickie, anyone know offhand what the cell bands are used in London and who the primary carrier/cell tower would be on a locked North American iPhone roaming there?

Had a user say his iPhone 4 was getting ‘no service’ whatsover in London, England. We were okay with the crazy roaming fees he would have incurred but I can’t help wondering if London uses the AWS bands (T-Mobile) that the iPhone doesn’t have.

Generally GSM 900 or 1800 for voice and 2100 for 3G data pretty much for all networks.

Take your pick of primary networks in London which one you pick up normally seems to depend on who your domestic network is partnered with abroad. Vodaphone, O2, Orange and T-Mobile are the main network providers.