s'ven, a brief note of update; it is possible that crystal palace park has now been handed over to the GLA who might be more interested in having motor sport at this venue again. I think that the Sevenoaks&DMC might be organising something?
Try checking their website at
http://www.sevenoaksmotorclub.com/
I'd imagine that there is a large number of people who live in the greater london area who (with sufficient advertising) would come to support events held here. It's definitely worth fighting for. Oh dear, I can feel myself being volunteered for something here!!!