Also try First Direct (they're a division of Midland). They have been excellent, and specialise in not only telephone but also internet banking. My impression is that generally their exchange rates/charges tend to compare very favourably with other banks.

When I mentioned to them that I was buying a flat in Moscow, they even wanted to offer me a Russian mortgage in roubles. In the end they couldn't, but that was the fault of the Russian Central Bank, not their lack of keeness!