I have not used them for fifteen years, but it's not a daft question at all. If you have an ATM card that works in the UK, you will almost certainly be able to go to an ATM abroad and get out cash. If you have a credit card that works here, it will probably work as well in shops etc. It's worthwhile phoning your bank/credit card company to alert them to the fact that you will be away, otherwise their daft systems might notice a strange transaction and block payment. It's always a good idea to get some of the local currency in the UK before you travel. The Post Office is good for that. Make a note of your bank/credit card peoples' phone number so you can phone them if you have problems when away.
Have a great holiday.