Robert,
Like you I am more inclined to the motorhome scene, but have to be careful about mentioning that around here. We swopped back to a caravan as we moved house to an apartment and I could not keep the motorhome in the parking area. So we bought a caravan and keep it in storage. Of course we can use the same car as both tugger and day to day use, but I do hanker back to the m/h. I had a Compass Mercedes coachbuilt from the 1980's and loved the payload at 700 kg plus. We could throw whatever we liked inside and still have allowance for a few crates of good wine to bring home. In addition, our kids were young and loved sleeping in the huge luton while we drove in the evening. It made long journeys a lot easier. The other thing that tempts me back is that you can get airconditioning in a m/h, although you do need a goood electrical supply or genny. I agree when it is very hot, that having that can be bliss at night.
Yes, the big issue is the lack of day to day transport when on site. It is more of an issue here in the UK as sites are often out of town rather than in France where aires are usually in towns or close by. Of course some of the new smaller van types on the new Sevel chassis are a shade under 6 meters long, but still nippy enough for daily use, especially if retired.
You have mentioned your better half has doubts about the interior colour and from that perspective I would be cautious, as she will always make adverse comments. Maybe better to wait and look around as the market is such that you will probably get a good deal whatever m/h you look at.