I agree KG. I always use Nationwide debit card but I am a current account customer there. The real proof is always in the FX rate given - and I have seen divergence greater than 5% from other banks. Nationwide fx rates have been consistently competitive. It is a shame they now apply the 1% charge but that is only £20 if you spend £2k on hols!

If you have the cash in the bank, I wouldn't personally open a credit card account. I also would never use it for ATM withdrawals where I would start incurring 27.9% APR interest from the moment of withdrawal. However, a combination of the two cards might be good if you can be bothered with the administration effort to save a few quid.

On pre-paid cards, I agree with Albert the Frog.