Taking plenty of cash with you from the UK will prevent any time-consuming difficulties with ATMs and banks. Outside of Marrakech it is safest to assume you will require Dirhams to obtain petrol, food, and accommodation. A tank of petrol will cost between 300DH and 600DH (depending on where you get the fuel). In Tafraoute there are two cash machines, and whilst they have proved more reliable than the one at Marrakech airport they have still been known to eat credit cards. If this happens, you can just go into the bank and retrieve your card from inside (as long as they?re open).