When I bought a pre owned van from a non franchised dealer I obtained a MBG warranty within the purchase. But there were certain exclusions in the TCs, cracked plastic body panels. I then used a Swift dealership Tilshead Caravans for servicing. They picked up a cracked rear panel and obtained authority from Swift to replace it at just under five years old. A friend of mine bought a new Swift from Highbridge but he too used Tilshead for service and repairs. But the big increase in ownership combined with supply chain issues and limited business resources has made life so much more complicated for prospective new owners like the OP who wish to buy a pre owned caravan from a non franchised dealership. Perhaps time to look at other makes. Adria have a good reputation as do Knaus.