After doing all the usual ones some of the other things I did were
Go to the Australian War Memorial and try to find your town on it.
Abbey Rd and walk back and forwards across the zebra crossing and annoy the cars.
HMAS Belfast was interesting.
Blue Plates are on lots of old buildings and tell of historical people or events that happened in that house, google for full list and hunt down what interests you.
Look for film sites, most of London has been in some film. eg Notting Hill, Harry Potter
Walk over the Tower Bridge and do the tour, watch it open, google for next time.
Imperial War Museum, Hendon RAF Museum, Cabinet War Rooms.
Greenwich 0 degree longitude, time ball, Flamstead House, Cruise down or up the Thames.
Rainy days for museums and Art Galleries.
Canary Wharf, traffic light tree
Plenty to do in London....
