Quote: sootyj @ August 10 2009, 7:17 PM BSTIf you get an Oyster card then the most you'll spend in a day is about fiver.
He's right you know.
Leevil, if you are in town only for a day and you don't want to use the Tube you could get a one-day bus pass for about £3 or £3.50 (can't remember exactly). If you're not going too far bus might be okay but over longer distances you will be screwed, and a Travelcard is a better bet (Zone 1-2 Travelcard is £5.60 after 9.30 and at weekends).
The one thing you *must not* do - alert all visitors - is pay single cash fares on Tube or bus. The fares are stupidly expensive (£4 each trip for Tube, for example).