You can get LED strips / ropes & the requisite transformers at virtually any brico shop in France, e.g. LeroyMerlin, Castorama, Bricomarché. If you're a long way from any of these, try amazon.fr or the web sites of these outfits. (Search for ruban led). As for wiring them in, the basic French wiring colours are green/yellow = protective earth; blue = neutral; anything else (e.g. black, brown, red, purple) is live. 1.5 sq mm will be fine, or even less if you already have it. (LED lighting currents are very low at mains voltage.) Actually doing it is going to be very similar to the UK; just make sure to keep all wiring inside suitable wiring boxes & carried in plastic tubes, either rigid or flexible, supported on clips. If/when you sell the property, the obligatory diagnostique will penalise any visible wires, even though they're insulated. Cables, i.e. insulated wires inside an insulating sheath, OTOH, seem to be allowable.
