I work in London very close to St. Pauls.
As said above, St. Pauls and the millenium bridge are superb, tower bridge also. On a clear day you'll be able to stand on the millenium bridge and get a shot of the Tower Bridge. There are some interesting sculptures in Paternoster Square by St. Pauls.
Also by St. Pauls there is
Postmans Park which was featured in the film 'Closer' starring Jude Law, Natalie Portman, Julai Roberts and Clive Owen - might be of some interest. Walk up the road, Little Britain, (yes thats the name of the road) and you've got St. Barts hospital which has a few interesting architectural pieces, and more importantly,
Smithfield Market. This is a fantastic building and it has some boards up with old pictures showing what it used to be like. It smells of raw meat though
Take the road opposite - St. John Street keep walking and you'll get to my work lol, but just at the bottom of St. John Street is VIC NAYLOR's bar which was used in Lock Stock and Two Smoking Barrels as JD's bar, and also in the remake of Alfie - very impressive (but expensive) cocktails in there (just incase you need to stop and wet the whistle
)
Carry on right up the road and you get to the Angel Islington (ala Monopoly) and the Angel has a very impressive metal structure of Angel Wings, an interesting photo opportunity. Walk west along Pentonville Road (ala monopoly again) to reach Kings Cross Station but more importantly St. Pancras, this is a very odd but impressive building.
Anyway go back to smithfields, walk east and get to the Barbican - the concrete jungle. People say its ugly, but its got some nice buildings - particularly weird is right in the middle of the drab 1970's tower blocks their is a proper very old looking church with what looks like original stonework!
Ok so keep going east past liverpool street and get to the Bank of England which imo is a very impressive building. Fairly near is Monument - this is to mark the great fire of London and if the monument was led down the top would be in pudding lane (where of course the fire of london started).
Now take the Central Line to Tottenham Court Road, and do a bit of shopping in Oxford Street. Then walk south, passing china town, and get to Trafalgar Square. If you're visiting London, Trafalgar square is a must. A great monument to a true hero (even if it is covered in pidgeon turd). In the vicinity, although a clicheed shot, Piccadilly Circus - very busy place but still quite impressive. Right next door is Leicester Square which is always a bustling place and where all the film premiers happen - your chance to snap Brad Pitt and Tom Crusie
erm..there's so much to see in London and its an incredible place with such a wide variety of places and different scenes to shoot. I've left off my mini tourist guide the millenium wheel, houses of parlament and big ben because I don't go there really - but nevertheless they are fantastic buildings and structures.
One of my favourite things to do is walk along the south bank starting at the millenium bridge and along till the Tower Bridge - I love the 1600's feel walking through the tunnels and the semi cobbled street, past the clink prison (had our Christmas Party there..AMAZING! free bar all night!), and past Vinopolis and what was the Cutty Sark.
Enjoy your time in London, in the City Centre you'll be fine just don't wander into the East End
Use the tube, take a taxi at least once, and watch the cyclists!! all of them have death wishes and I've almost been mowed down on tons of occasions :bang:
A wander from Waterloo to Tower Bridge is great for buildings, there are so many oppertunities it will probably take you most of the day to do a walk that would normally take an hour or so.
well done they are awsome 
