The building, situated between Belsize Park and Hampstead in Lawn Road, was the first Modernist designed building in the UK and is now a Grade 1 listed building. They are compact and practical inside, and were originally designed "with special reference to the circumstances of the bachelor or young married professional or businessperson".
They were also home to Agatha Christie 1940-46, something which apparently local people know but I didn't. They were rennovated in 2001 and sold and rented to key-workers, indeed the party host was a paramedic.
More information here on Archidose here
http://www.archidose.org/Aug05/082205.html
Google Street view of Isokon Bulding

Photo by Steve Cadman