Are you based in UK as most banks provide free use of debit cards?
Visa and Mastercard are widely accepted in UK shops - American Express less so.
If you are visiting you might want to look into a prepaid currency card or ask around where you live for the best bank card for travellers - I know that some banks here are better than others when we go abroad.
As you are asking on the UK board you are asking people whose local currency is GBP and therefore don't need to exchange money while we are here so might not be the best people to help you.