Is there a social group for people with aspergers syndrome in north london?

My CBT doctor suggested that it would be useful for me to join a group but she could only find groups based in ealng and kensington. I don't mind travelling to one of those places (although I find public transport hard work) but is there a group in the north london area that anyone knows of? Also do these kind of groups mind/understand if you find you have to leave at very short notice?