Bear in mind this caravan is going back to the manufacturer for repair.
At least the manufacturer should have all the correct materials, and because it will one of only a few returned to them it is likely to receive very careful attention. I would like to think it might be repaired to a better standard than when it was new! It will have to be described as manufacturer refurbished or equivalent wording, and it will probably be offered with a full warranty package. - A virtually new caravan built with real care, at a knockdown price. Potentially it could be a cracking (no pun intended) result for anyone who is offered it.
Unfortunately I don't know if the full history will follow the van to the dealership selling it, because the contract rules between the manufacturer and the dealer are not controlled in the same way that retail sales to end users are (Consumer rights Act).
So even if the the potential purchaser does ask the right questions, the dealer may genuinely be able to say we don't know what faults it had.
However as I suggested above, a manufacturer's refurbished product has every chance of being as good as it gets, in terms of function, and in this case water resistance, so provided it looks good, it may be a better bet than a brand new one.
Even though it might be a good deal for a new customer, it still is unsatisfactory that the original customer has had so much grief with the caravan.
With regards to using the old SoGA and newer CRA, I strongly urge customers to remind sellers (not just caravan dealers) that they haven't ordered faulty goods so when they do go wrong use your consumer rights to get what you have paid for - goods without faults. The more pressure customers put dealers under in this regard will force them to live up to their statutory obligations, and correspondingly make it more difficult for manufacturers to ignore design and productions and quality failings.
Lets make 2016 the year that "the customers turned" and bite back to stand up for what is rightfully theirs - better and more consistently built caravans.