Check out the Millenium wheel, or London eye! Worth the trip, book in advance.
While your down there, St Pauls, Houses of Parliament (Big Ben) and Tate Modern are all nearby...(Try the slide in the Tate!, google it)
By all means go to Oxford street, but that and Totenham Court road are a waste of time now. Nothing but overpriced tourist traps that you would do well to avoid buying things in.
Check out a show in the West End, Visit Harrods in Knightsbridge, walk along Hyde Park and there is the Science Museum in Kensington (Exhibition Road). There are also about 3 other museums around that area. You can see the 10,000 year clock in the Science museum.
Go to Nottinghill Gate on a Sunday Morning and check out the Antiques Market/Street fair.
Above all, get an OYSTER card and pre-pay on it, will save you LOADS of money. Use the bus where you can so you dont miss the sights. London isnt actualy that big and the tube is hot dirty overpriced and you miss everything above ground.
If you wanna share some Ameo software give me a shout, im a London Local.
HTC Athena (T-Mobile Ameo)
Magnets are great, now my keys stick to my phone.
"Of all the things ive lost in life, I miss my mind the most."