Where's best to buy a second-hand wedding dress in London?

[WildItWasFurious]

Getting married next year and would like a sort-of traditional wedding dress (i.e. long and white with sleeves, but don't want a train) but don't want to break the bank for something I'll wear once. I'm thinking I could get it altered to fit me exactly. I'm happy with a second-hand one, but want to be able to try it on so not keen on buying online....

I am clueless about clothes in general and wedding dresses in particular so any help would be much appreciated!

My sister runs a charity shop and they have a large amount of dresses donated . Some are beautiful!! Maybe ring round and as a few ? My sister has them all photographed and labeled so you can look in a book... I think it's a brilliant idea !