Hi Pascal, I'm sorry it's taken me so long to reply with an update!
The good news is things are going well, we're settled and things are fairly normal.
For insurance, we use Aon InsurXpat. They speak English (ish) and the premiums are okay. I pay about 350 euros for an agreed value classic/collector's car policy for the Lotus. The recognised my full no-claims bonus from the UK and gave me the full 50% discount in France. We insure our daily drivers there as well.
Banking was a bit of a surprise - in the UK it's free, in France it costs over 200 euros per year! We started with HSBC who had an arrangement with my work to give us free banking, and they spoke English and had English online banking. When they started to charge us (and because their service is rubbish) we moved to BNP Paribas who also have an arrangement with my work to give us free banking for a few years. They also speak English in our in-work branch and they have English online banking but not as good as HSBC; the service is much better though.
For house insurance we just found it using price comparison websites like we would in the UK, compared the small print and they've remained the cheapest for four years.
Parts availability is okay. There are online companies that stock most of the Opel/Vauxhall and other off-the-shelf parts, and other more specialist parts can be ordered from the UK or USA, or by phone/email from Lotus dealers in France. It isn't as easy as in the UK but it's not too bad either.
I haven't had to pay for any work on the Lotus yet, I've done it all myself. I've paid for work on our daily driver (terrible Fiat Grande Punto that is stereotypically Italian in its build quality) and found it a reasonable price, which was a nice surprise.
For LHD dipped beams I fitted the yellow ones I got from Lotus Aftersales and the main beams I left white. My car passed the CT without problem both times, only small advisories which if I'd been in the UK would have been a fail! (headlamp adjustment, wheel bearing). And the emissions has proven to be no issue, it easily passes the test whereas in the UK it is close to the limit. My CT experience explains the number of cars we see in Provence with barely/wrongly working lights (flashing brakes when turning?!) and filthy exhausts.
Elan knowledge? Thankfully I've not had to find out! The car is listed in online parts/insurance websites, but apart from that I suspect it is unknown.
For breakdown cover I use ADAC rather than the cover that is normally included in the car insurance. I think ADAC is better standard of cover and is usable with any car, like the normal AA/RAC cover in the UK, whereas the stuff that comes with car insurance in France is only for the specific car.
Registering the car in France was a little tricky. The car was made before it was on sale in France and the UK CoC wasn't acceptable to the local prefecture office because it was before European type approval became the norm. I had to explain to Lotus UK how to complete the French CoC form (it's changed in the past few years) and I had help from people at work to communicate with the person from the prefecture (who, it turned out, wrote perfectly fine in English, I later discovered). In the end it all worked out, but (like all admin here) it took much longer than I expected it to.
On that point, almost everything takes longer to do here because 1) the processes are more bureaucratic, 2) the processes are different from the UK so all the preconceptions of how it will work are wrong, 3) I don't speak/hear French well and it's rare for things to be done by email here, unlike in the UK. Note that I'm sure that French people moving to Britain experience exactly the same frustrations!
Roads: Outside of July and August the roads round here are generally clear and nice to drive. In July and August there are too many tourists for it to be really enjoyable. The gorges du Verdon are awesome, but not really for driving quickly around, more for admiring the view.
When traveling across departement borders the road quality (especially on minor roads) can suddenly change which can be a nasty surprise! I notice this going between Var and Alpes-de-Hautes-Provence, the 04 roads are often very poor in comparison to 83 roads!
The speed bumps in France are incredible, some of them are bigger than an Elan! Thankfully speed cameras and policeman aren't difficult to avoid really, certainly no worse than in Britain.
Driving in France does require one to keep one's wits about oneself because there's always the risk of being killed by yet-another-Frenchman/woman-thinking-they're-Francois-Delacour/Michelle-Mouton! KSI stats in France are ~twice as bad as in the UK and it's fairly obvious why. We've noticed that there's a marked difference between the driving before lunch/apero time and afterwards - 12:30 and 6:30 are typical times for people to be driving like lunatics because they're late for food/booze, and when they're on their way home they're much more sedate but even less likely to stay on their side of the road.
Weather: obviously the weather here is considered to be amazing by everyone who comes here on holiday from the UK, and in general they're right. However, driving any convertible car in the summer in Provence is almost impossible in the afternoon, because the sun is strong enough to melt lead. Winter is very cold due to the clear skies and continental cold air mass, -10 degrees C is common in the mornings. When it rains it really rains. On balance, it is better than the UK, but not always.
Right, that's a long enough essay, I hope it's useful to some folk! And if anyone needs a hand drop me a PM, I'm happy to try and help

Cheers,
Will