... As long as you take cash out of the machines with a debit card (or pay in shops with one) and not a credit card, you will get a better rate than buying currency before you go
Rob - you are much better off doing foreign transactions on a credit card, not debit. The exchange rate (if both cards are say Visa) is the same. If you are purchasing goods there is no interest. If you are drawing cash the charge (often 1.5%, minimum £1.50 so worth drawing £100 or more equivalent at a time) is the same. But on a debit card the amount goes from your account immediately, on a credit card you have some weeks to pay.Then again, if you don't pay your credit card in full each month all bets are off.
But certainly agree travelling with just a (credit) card is the way to go.