Forget about any manufacturers warranty, this caravan is way out of that period.
its 22 years old (which is ancient in caravan terms) and it oʻhas been repaired, by the dealer it was purchased from, at no expense to the purchaser. So the dealer has both acted responsibly, and very reasonably.
My view would be that it has now been professionally sorted out to comply with current legislation, and that work must be guaranteed by the dealership.
I would consider that the dealers have done all they possibly could and that the caravan is now 100% safe to use.
Rather than get involved in all sorts of legal arguments, and associated stress,simply move on, accept that the caravan is now up to standard and get on and enjoy it.
I would suspect that any small claims court would view it as I have done (because all is now correct) and not enforce any replacement and or refund.
If you are still looking at going down the legal route then you simply MUST obtain professional legal advice before doing anything as you could end up with a very large legal bill, and many months of unecessary stress.