Brant;

Alot of good advice here already, but I'll chime in with my 2cents anyway... I find that london and paris are not particularly crowded with large buildings and most of the tourist areas have plenty of space to back up so a UWA is not always necessary (although there will definitely be lots of people in the shots). I've been to London quite a lot (we lived in the UK for a short period) and most of my london shots were taken with a Rebel Xsi and 15-85 lens. But I'll also add that a 70-200 lens is great there as well. You'll find that there are numerous areas where you can shoot the iconic images (london eye, buckingham palace, tower of london, parliment, etc) from a distance away with a longer lens and give a different perspective. Similar to the shots you linked from Paris (although my Paris trip was pre-dslr so I don't have direct experience with lens selection there).

Someone also suggested leaving the tripod home, but I strongly disagree with that! May not be allowed inside most churches, etc. but it is great for longer exposure at night. Lots of buildings are well lit at night and make for great photo-ops. Shouldn't be any issue finding space to use a tripod in most areas, especially after dark.

If you have specific questions about things to see in London I know the city fairly well from a tourist perspective. Feel free to PM me. I'll also see about posting some of my London shots to Flickr...

Stephen