I've noticed in the past that Classic Car Weekly often list autojumbles. It might also be worth contacting people who organise general classic car shows in your area, as quite a few also host autojumbles.
As for fleabay? Jumblers seem to be using this to work out the pricing for their parts, if you ask me. A few times recently I've tried to haggle and got "I can get more than that for it on ebay". I also look at the stalls that are inside last. I've noticed that all the traders who are outside in all weathers, often offer a better deal. But then, they're not paying the extra to be inside are they! :laugh: