Be careful though. If you end up in a semi-rural area or an area with few tourists, you could have problems with your US credit card in stores here. The UK has something here called 'chip and pin' and some stores won't accept cards without them and US cards don't have this feature.
Also, you can have problems with the US cards online when using UK sites if, like me, you keep the US card with a US address (mine is my mother's address).