Total 10W50 (and Elf competition 10W50) remind me the good old time of Citroen AX Sport, BX 16 soupapes and Peugeot 205/309 GTI. But back in the time it was considered a very good street oil for sports car, when Yacco and Labo 15W40 mineral or semi-synth was the norm.
I see Total 10W50 has evolved, nothing exceptional nor exotic additives but it now carries both SN and CF rating (ACEA A3/B4)...and it is quite cheap! 33€/5L here. I like Mobil 5W50, but is a bit more expensive..and on the heavy side for where I live (max temp today : 18°C, and it was a sunny day. Nice August weather).
I've tried Carrefour 5W50 in the past and I'm not 100% convinced it is still Mobil 1 rebadged, but who knows? It is made in the EU, and there's not that many 5W50 oil makers...Elf, Mobil, Motul, etc. It was ~32€ last time I bought it.
I don't think 5W vs 10W will make much of a difference with the temperatures you are experiencing, but I'm not sure how redesigned the HDI 16V are over the "original" 2,0L HDI 90/110cv. A friend of mine still had a 110cv 2,0L HDI, ran year round with semi-synth 10W40 (and 20K OCI)...270000Km and still rocking.