i searched all the advertising sites and went to glossop caravans to have a look at prices of vans the same as ours, fortunately i have a good relationship with glossop so they advised me of how much to advertise my van for which helped a lot. unfortunately since caravans are so sensitive to "user use" no van is the same as the next regardless of age, ours for example is in imaculate condition and glossop said it would go straight on the pitch with no work needed it didn't even need a clean so it is valued at top money they showed me a similar van that had been part exchanged but was in average condition and it was £800 less than ours. glossop where desperate to get hold of my van due to its condition but being a dealer they could not offer me the money i wanted.
i would search all the web sites and visit your local dealer, ask them how much they will give you to just buy it then add around 15 % and you have a good private sale value.
bye the way if your looking for a fixed bed ours is advertised on practical caravans classifieds site, not sure how much you want to spend but i guarantee you won't find a better one outside of a dealer or new, we are selling it only because we have bought a small farm in brittany and spend all our spare time renovating the barn for our retirement home so the caravan is no longer used. coachman vip 530/4 have a look :~).