For me one big issue would be the different regulations. For instance, any British sparky installing a ring main is doing it right in the UK, and breaking the law in France. A Brit living here and working as an electrician would get that right - a mate coming over from London might not.
Just starting my own restoration and I’m very much with David - I’ll be working with Maisons Paysannes, using traditional techniques. There are good engineering reasons for this - traditional earth based render on the facade allows the walls to breathe, while cement render keeps moisture in and eventually leads to damp problems, for instance - as well as the desire to be authentic.
What I find refreshing about the French attitude is that architects rarely seem to see a clash between modernity and authenticity. They’ll talk about traditional masonry techniques and building forms, and then introduce the subject of solar panels or the idea of adding a completely modern chrome and steel extension. So while the structure may be traditional, the two massive fireplaces certainly won’t be the only heating system employed!