A number of years ago I was there in March and the weather was not the
best. Still there is a lot less people so that is a majour advantage.
If you are looking tickets for the theatre you can go to Leceister Square
and see about 1/2 price tickets.
Some of the sites I remember the most are the British Museum, War Museum,
National Portrait Gallery, St Pauls(all 425 steps up to the top) and
Westminister Abbey. I
What specific interests do you have? How long were you planning to
go for? There is just so much to see in London!
Hope this helps!
Tom London, Canada