That's great Dan, well done on getting it through with no advisories.
Re. 30mph; have you tried 3rd overdrive? That would split 3rd & 4th which might be just right.
Soundproofing makes such a difference, doesn't it? we put a lot in to Patrick's Carawagon, including bulkhead soundproofing before the engine went in. Even door cards make a big difference.
You can carry out a normal conversation at motorway speeds, and that's with a 200TDi

Mine is a bit noisier as I haven't really got much to deaden the sound in yet.
Good luck with the heater search - hopefully you will get a couple of weekends away before next year's show season
We're looking forward to seeing it in the flesh
Cheers,
Robin.