In major cities, credit cards are accepted in all shops, restaurants and hotels. Providing you have a pin number, you will of course be able to withdraw money from ATM´s. In addition to high street banks, these will be found at supermarkets, train stations and usually at gas/petrol stations.
Do not take the risk if you´re heading to small villages - there may be no cash machine and b&b´s might refuse credit cards.
Mastercard, Visa, American Express and Diners Club are the most widely accepted.