My caravan had outstanding finance

I have owned my van for 2 years and when I came to sell it I discovered it had outstanding finance. I purchased it at auction and had no way of checking the CRiS at the time of bidding. After selling it on Ebay for £6000, the buyer did a hpi check and withdrew from the sale. It has taken several weeks to sort the problem out and I lost at least 2 sales in the autumn of last year. I now want advertise the van for sale this Spring but obviously it is another year older and will have suffered depreciation. Would it be reasonable to expect that it has lost around £200 (or more) over the winter? The van is a 2005 Abbey Freestyle SE 540/4. I'm sure there will be someone with eperience in valuing caravans reading this. Any thought or advice would be helpful.