London Abandoned / Urban / Hidden Locations

Hi Folks, I'm in London for the week staying with my brother. I want to get off the beaten path a little and find some good locations. I'm a big fan of abandoned locations, urban photography, etc. So any pointers or suggestions would be great. I think there was a website dedicated to exploring hidden locations of major citities but I can't find it.

Thanks in advance.
Adam.
ashepp@gmail.com