I feel your pain and have the same t-shirt too. We had always had second hand vans (12 -24) months old and had five of them giving us not a days problem on any of them. Then we decided to treat ourselves and go for new. Whilst not having a damp problem as bad as yours, nevertheless we had a similar last, damp at first service, complete failure of the Drawbar Unit, failed alarm, failed charger, split bathroom door seals, wardrobe trim fell off, damaged wheel arch done by the dealer, who then tried to blame us, and so on and so forth. Vowed on all the saints I would never buy another Swift, but guess what, we traded it in for a Swift, 12 months old B)
Never again will I buy new. My feelings are that most niggles a caravan will get will be evident within the first two years, let somebody else sort it out.