If you're confined to only London in the UK, then you could try the Imperial War Museum at Lambeth
http://london.iwm.org.uk/, this page covers the aircraft on display
http://london.iwm.org.uk/server/show/ConWebDoc.1470, as does this
http://www.kiwiaircraftimages.com/iwm.html, but there is so much more there to see other than aircraft.
There's also the Science Museum, see here for photos & info
http://www.kiwiaircraftimages.com/science.html
Both museums could be visited in one day, more so if you're only there for the aircraft.
If you can get out of London, then you MUST visit the Imperial War Museum outstation at Duxford,
http://duxford.iwm.org.uk/
Why not pop over to the FlyPast Historic Forum
http://forum.keypublishing.co.uk/forumdisplay.php?f=4? If you post the same question over there, you'll get lots of feedback, and maybe a few more ideas, plus I'm sure people will put up some of their excellent photos to give you a taster.
Geoff.