Phew! Problems with a Hymer motor home - any help gratefully received

Hello all. I am afraid this is going to be a long post - so get a cuppa first!

We emigrated to France 9 weeks ago. A week before we left the UK hubby traded his beautiful sporty SAAB estate for a Hymermobil Starline, 2002, (I think!)
I have no comment that is printable on a lovely page like this.

So, we packed it with the stuff that was going to go in my Audi and his Saab - it did very well down to Dover, and very well until about 20km from our holiday home in Deux-Sevres, where we were planning to spend a few days before heading down to 86 where we are now living. I was keeping a weather eye on him from my rear view mirror, as I had Sat nav and he hadn't and he just got slower and slower - so I stopped, he stopped. He said there seemed to be a problem with the automatic gearbox - it wasn't shifting up into 4th - so we limped to our house in dept 79 and asked a mechanic friend in the village to have a look if he had the time. He couldn't do anything for a few days, so we left him the keys - decanted a whole mountain of stuff into the house and left it there and came down here in just my car - with the bare essentials!

When he tried to look at it . . . the starter motor was b******d! So, we rang the RAC, they came and hauled it off to Vihiers(49) and we were straight on the phone to the cowboy, sorry car dealer, in UK - we had a statutory 12 month warranty, and we had also purchased an extended warranty too.

He has been a total tool - digging his heels in, asking for the old starter motor to be returned to UK (we did)- galling at cost of fitting it, asking us to return it so "his guys" can fix it (!!!) The RAC have been brilliant, liaising between garage in Vihiers and Delboy in UK, and keeping us up to date. The reconditioned starter motor has now been fitted and they have done a diagnostic this afternoon of the gear box problem. There is a problem (really?) However, they do not touch automatic gear boxes. The garage want us to go and pay the bill (absolutely no problem doing that) and take it away - but to where? And with it only going up to 3rd gear, not 4th

So, first of all if I described the problem on here, might someone be able to throw any light on what it could be?
And secondly, does anyone know of a garage in department 49, or 79, or anywhere within a slow (only up to 3rd gear) driving distance of Vihiers which they know (and trust) could investigate (and then fix) an automatic gearbox on a Mercedes 2.8 Sprinter engine (which is what the engine is)
Hubby has already dictated to me what I need to describe as the problem, but I'll not bore everyone with that unless someone gets back to me and asks me to describe it.
I appreciate any advice/guidance etc you can offer. Thank you very much.