Hope it's OK to put my 2 cents out there, even though I am in the US. Just checking out the UK boards for my trip to London in May.
In May I am Seeing:
Billy Elliot twice (tickets on sale Nov. 12!

Can't wait)
Lord Of the Rings, Dirty Dancing, Mary Poppins, Dirty Dancing, Wicked, Evita, and hoping that the History Boys will be extended so i can catch that as well.
Back here in the states I have seen:
Rent (98 times-yeah I know, I have a problem)
Hairspray X 8
Wicked X 6
Phantom X 3
Aida, Lion King, Chitty Chitty Bang Bang (loved it!), Mamma Mia, Brooklyn, The Producers, Les Miserables (Colm is incredible), Chicago, Dirty Rotten Scoundrals, Kiss of the Spiderwoman, Tick Tick Boom, Swan Lake, Ave Q, Caroline or Change (incredible...go see it!), Miss Saigon, and most recently The Beatles: LOVE by cirque de solea (or however you spell it)