There is no place like London. Tour around the city on a double decker bus, ride the underground, float on the river Thames, or just walk. Scenic bridges and well known tourist sights are everywhere.
If you have lots of money try shopping at Harrod's. I purchased one delicious truffle there for the equivalent of $4.00, just to say I did. But not to worry, there are plenty of experiences to be had in London, even for the money challenged.