I have had a Nationwide Flexaccount since they were first opened 20 years ago and have always used it whilst I am abroad purely because of the lack of charges. It is true also that there are no extra charges when using the Nationwide's credit card whilst abroad.
We got back from 2 weeks on Rhodes last Wednesday. I have just checked my online statements and the rate we got on withdrawals fluctuated between 1.478 and 1.492 whilst we were there.
As nothing other than a satisfied customer I would recommend the account especially as you can use an internet cafe whilst abroad to ensure that everything is fine with any account that you have with the Nationwide.