Originally Posted by Andrius
Well, it used to be that withdrawing foreign currency abroad on your DEBIT card was the cheapest way.
Not anymore: 
many banks (incl. Barclays and Citibank) started applying the same charges for debit card cash transactions abroad as they do for credit card transactions.
I can't repeat often enough the tip to use
Nationwide Visa cards when outside the UK.
Nationwide Visa! Nationwide Visa! Nationwide Visa! (that's enough repetition for now ...)
0% foreign use fee and 0% currency fee for the credit card - and 0.5% cashback. 1.5% foreign use fee and 0.% curency fee for the debit card.
It's a no-brainer.
And for you Travelex travellers cheques fans, the Nationwide debit card does not charge extra as a 'cash' transaction at Travelex UK.
www.nationwide.co.uk.