Claire. As it's an early model I would suggest that you give your namesake Clare a ring at KOOL Classics.
Yes, a little way east along the coast from you but they are the best around particularly for older models.
There is Leisure First in Poole but they might not be interested in looking at it for you.

That's a first

Did you pay for a service when you were warned about the damp?
If not, speak to Clare on the phone and explain what you've been told and mention that we (Eribafolk) have suggested you contact her.
She will service the van if it's not been done or will invite you to bring it in so they can look at it.
We believe that the original guy you took it to doesn't have a clue about Eriba construction.
If you can't see damp or smell damp there doesn't sound as though there's much wrong with it. At most a re-sealing of the waist rail and perhaps new window gaskets.
Randa