The problem is that from an insurers point of view a caravan is economically repairable if the cost of the repair will be cheaper than the replacement cost in these cases. Possibly the underwrites would take a generous view and replace but I have no experience of any claim at this level with the CAMH so cannot be sure how they would act, but it is a possibility particularly with the cheaper policies where cost are shaved to the bone. I think this is mainly theoretical, as getting damage that costs between the current value of the caravan and its replacement price is very unusual.
As I understand it they will leave you to negotiate for the new caravan provided you get a decent deal and will allow you to buy something different if need be if you decide to upgrade if you pay the difference in cost.