Thanks a lot DrG

, it will be a great weekend.
Read on London Expo board:
Dear Sir/Madam
I am sorry to advise that there will be engineering work taking place on the
Jubilee Line between Stratford and North Greenwich throughout Saturday 16
and Sunday 17 October. There will be no service in both directions between
Stratford and North Greenwich. Replacement buses will operate between
Stratford and Canary Wharf calling at West Ham and Canning Town, but not
North Greenwuch. If possible, please use alternative London Underground,
Docklands Light Railway or National Rail services, which should be operating
normally.
Best Wishes
Gerard
London Travel Information
So I asked how we could go to London Expo, and nice people answered me, telling that:
"You can take the "Waterloo & City" line to Bank and switch there to the "DLR" (Docklands Light Rail). I think Custom House is the station to leave for the ExCel."
Hope that it will help you too