Here is the best decorated Halloween house in London, at least that I know of. There's eerie music, fog and excellent creepy lighting at night. It's only a few blocks from my house, and it is the only place my kids insist on visiting at Halloween, which at their age is like the Superbowl of all special days.
In addition, for all you "where's the bike?" types, I've been saving this little chestnut:
Enjoy this most excellent of special days.