London is so vast I end up spending hours travelling on trains. They are by far the best way to travel around on and are always full of weird and wonderful characters.
Tucked away down a cobbled alley behind Russell Square Station, The Horse Hospital, a converted stable, is a unique and totally independent arts space specialising in underground and experimental media. The gallery space itself (known as The Chamber of Pop Culture) houses unusual exhibitions, film screenings and other events.
It's a members-only library but you might be granted access with a research request. The writer's room is great but there's a few special, hidden corners among the bookshelves to tuck yourself away in.