If you want a peaceful day out of the busy city, Highgate doesn't really feel like London. The cemetery is interesting and peaceful, there's a tour of the old half which is definitely worth the money. Karl Marx, among others are buried there.
Great selection of books and magazine with a big focus on rare. out-of-print books Japanese photography. Can sends hours in this little shop. I'd try to avoid on Market day (Saturday) if you want to have a good look as it can get a bit busy for such a small space.
Hotter than hell, but always a good night had. It can be whatever you want it to be - restaurant, pub, or club, has good outside space and rentable rooms, and plays an interesting mix of music to an interesting mix of people. The building is actually kinda beautiful too.
Bowling alleys, karaoke rooms, pool tables, arcade machines, this is basically Feltham Bowl for adults. Part of the holy trinity along with Max's Sandwich Shop and The Faltering Fullback