...and don't forget...
I'm surprised no one has pointed you at Ken Ellis' "Wreck and Relics" book. It's about to be re-issued (update 24?) and is the bible for UK museums and other aviation related sites.
Also, this months Flypast has a handout on UK museums as well.
Between the two, that should give you more than enough to think about.
One last suggestion: it may be an idea not to come over during the Olympics. The roads and everthing else around London will be jammed totally....