We were in London this past June, only for 2 nights, prior to going to Morocco for 3 weeks. I would suggest getting a pass on the "Underground" also known as the "tube". I thought it was easy to figure out. You should be able to get around to all the tourist spots. We also got a 24 hour pass on the open air double decker bus. That was ok, we rode the complete loop, just to see the city. Other than that, we never used it. We did catch a train at Waterloo, to go to Hampton Court, about 30 minutes outside downtown London, that was very easy. I would not suggest driving in London, there is a congestion charge for driving in the city, during primetime. Plus, you will lose lots of time, sitting in traffic. I have had the pleasure
of driving in London, when I was there in the Air Force. It was very stressful, I thought. Anyways, other people should have some advice, info. What area are you staying in, what hotel? You will love Europe, it is magical. I was lucky enough, to have lived in Germany for 2 years, before the wall fell, when I was in the Air Force. Europe is awesome.