Ah Mikie!
First, you could have gotten an all day, 5 section 'underground' or 'tube' pass for like 5 pounds (probably 6 pounds now). Basically, London sections radiate outwards from the city and are broken out by some sort of distance measurement. There's a special name for this pass, but I forgot what it was called. Sucks, I really should have given you a 'tips' guide, but I didn't remember you where headed to England as well.
Second... London is very easy to walk around... no seriously! The suggestion to walk isn't very far-fetched for the masses there. From Waterloo, you can pretty much walk anywhere important, and with an extended walk (about 30 mins) you could even reach the other interesting areas... for tourism that is. Oddly, when you first start discovering London, you would just hop the tube and end up at the location. But once you start walking around, you find out all the places you where going were just hiding around the corner and it was faster to walk than take a tube!
hehe, such is the reason I love London! That and "Ciao" the Italian ice cream bar. *drools*
Hey, when I get married in France, and of course you'll be there, we'll take a trip to Londres (as the French call it) and we'll sight see and hit a few discos.
Cheers,
John