Normally in France it would not get cold enough to warrant engine warmers unless you are in the mountains. It will help if the aircraft is hangared and if you can do some sort of engine pre warming that would be good. Pulling the prop through may help slightly, but probably not a lot -IIRC this mainly came from older engines with cylinders at the bottom of the engine - especially radial or rotary engines. Another thing to watch out for is if you have electric flaps and the checklist has you running them up and down before start - leave it until after starting the engine, especially if the battery is slightly tired, cold weather is not great for batteries and anything you can do to help that is a benefit.