I took an hour last week in London to visit Pollock's Toy Museum by Goodge Street. It is a fascinating place, with a windy staircase and rooms piled with old toys. Fascinating, and also terrifying. I wouldn't recommend it to anyone who had nightmares about Toy Story, but I found the old toys and toys from around the world really interesting. If you're not prone to toy nightmares, you should definitely go next time you're in London.
If you're interested, you can find more information about Pollock's here!