There's oodles of things on in little galleries around Bond street I noticed in the most recent issue of B&W Photography magazine. Luckily you can do 3 exhibits in one day and I have a feeling they're all free to go look at. I highly recommend the Linda McCartney exhibit - beautiful huge platinum prints done by 31 Studio but you can tell the original source of most of the images were nice, gritty 35mm film. It's not completely full of celeb pictures either.
When I went to the Man Ray,etc exhibit the other week, it was a few days before the street photography exhibit opened