So...

Lucky girl!

I'd start with a pint of Strongbow. Then check out the British Library...when I was there 4 years ago, there were some awesome exhibits. Buy lunch at a Tesco or a corner market and eat in a park. Later, go to a play and/or a pub for more Strongbow or your beverage of choice.

(The Tower of London, Westminster Abbey, Buckingham Palace, and Hyde Park are nice places to see, too.)

Well, since you're time is so short, I'd probably not go with my favorite thing when I was there for two days, unless you have a thing for astronomical and geographical history: boat trip down the Thames to Greenwich. One "down time" thing I enjoyed was lunching in Trafalgar Square, doing my best to avoid the pigeons. I also enjoyed walking through Hyde and Green Parks. The tour of Parliament was interesting, but I'd like to go on a tour of Westminster if I ever go back. If you're looking for some exercise, climb to the top of St. Paul's if they're still letting people go up.

I've lived in London for 22 years (you get less time for murder). I would start off on Friday with breakfast, then head off early so you can enjoy "Rush Hour". After 30 minutes of having you face thrust into some sweaty Betties arm pit for 30 minutes I would fall out of the train at Charing Cross and briskly walk down to the british Museum. This would take most of the day to go around. Friday evening would be spent going around some of the Samuel Smith pubs before staggering into a night club for a hard night of drinking and chasing the fairer sex. Departing the club in the small hours I would then wind up a couple of illigel mini cab drivers by asking how much it would cost to get to Bimbleford in North London, then ask for the exact route. Once they have told me their route to this fictional place I would tell them to F.O and then run away giggling like a school girl. Once sobbered up on the night bus home I would crash out on the sofa till 09:00hrs the next day. Saturday would be spent chilling out along he Thames and seeing the sights. Giving tourist the wrong directions to places. Then in the evening I would find a dirty underground rock club to go to and slum it for the night. Sunday would be spent on the bike, cycling around the City (Finacial are of London) which is normally empty of every one and every thing - looks like a scene out of 28 days later. Oh I would also take lots of photos.