I've found the organisation that have set up uses for empty shops in Brixton. They're called Spacemakers. It looks like they are working in other areas too. Not had time yet to go through the site, but thought I would post straight away.
Time is ticking on. The Turner is opening in spring 2011 and we're still struggling with empty shops and a lack of affordable studio space and retail for creative projects. These guys seem to have found a way round the old problem of rates payable as soon as a property is used, which makes it difficult to attract people to rent them out in areas where there might be low foot fall and also low sales.