Maybe it's the architecture, people's manners or the side streets, unchanged for a hundred years, that you can stumble into, but London always feels close to it's own history. For a taste of that queer history, check out London Walks, which has started organizing weekly trips around Oscar Wilde's London.
With more drama in his personal life than in his wildly -- pardon the pun -- popular and pun-ridden plays, poor Wilde's London life was as full of slander and publicized trials about sodomy as it was of his biting witticisms and a thriving LGBT scene.
If you're in Londontown before September, you can also go see Matthew Bourne's new production of Dorian Gray at the Theatre Royal Newcastle and make a Wilde marathon of it.
I never travel without my diary. One should always have something sensational to read in the train.