Nationwide definately, but thought that I would add that if you want to get cash from ATM's you will need a Nationwide Flexaccount with Debit Card.
I opened an account only for use abroad and the guy in Nationwide smiled when I said this is all I wanted the account for. He said they have lots of customers the same and they did not mind. Just keep a small amount in the account rest of time, say £50 to keep account open.
Nationwide credit card is only OK for purchases like in UK.
P.S. Even though ATM's in US say a charge on screen for using ATM, Nationwide does not charge so you do not pay extra. Used an ATM in a hotel and it mentioned a $2.50 charge but it was never deducted by Nationwide.