Much as it pains me to say this, Waspman is an expert in this area. Halifax Clarity card does not charge for normal transactions, such as having supper etc., and I mostly use mine for that. Getting cash abroad is basically a very bad idea, so for cash either get it at home for the best rate you can find (usually TravelFX) or, as you do, take a prepaid card.
You can change GBPs to euros at San Stefano Travel, where the kindly, intelligent, helpful, knowledgeable and beautiful women (hope you're reading this Aline!) will charge 2%. We usually take maybe £200 in GBPs with us, becauseif you don't spend them you use them at home.