Just a quick note for those of you in the UK. Nationwide credit card (Standard Cashback VISA Card) doesn;t charge any commission on foreign purchases. Their online statements are pretty crap, but at least they don't charge commissions. The rate seems pretty good too so I don't think they are milking it that way either.
I know people may say its not worth it, but compared to AMEX's 3% I save about £90 year (I spend about £3k/pa on foreign purchases).