Woodstar,while I can empathise with you on this one, unfortunately you have fallen foul of the sales patter.
I'm just guessing but I suspect the seller offered to lump all the accessories into a very low deposit deal for you. This is fien unless you come a cropper as has unfortunately happened to you.
It's so easy to be wise later and hind sight is a wonderfull tool, but cash is king I'm afraid.
However there are a couple of things you could do.
First of all, try declining the first offer from the insurance, then try it again on the second offer. That might get you closer to break even.
Secondly, contact the finance company, explain the situation and ask if they could accept a lower settlement figure on your finance. Don't divulge the insurance offer value and see what they come up with.
Finally, you could keep up the finance payments, and buy a van with the insurance payout. This is not strictly "legal", but it does get you a van without loosing all your ambitions.
I'm afraid only the insurance companies and new van sales come out on top. As you loose 30% of the value of the van when you roll off the fore court and the insurers always offer bottom price unless you pay over the odds for a new for old policy which, you might not use as you will of had the unlucky prang now.
I do appologise if my post sounds a bit cruel, but the hard facts do sometimes hit raw nerves.
I do hope you can come out of this with a caravan and are still able to enjoy a wonderfull hobby.
All the best.
Steve L.