Affordable heating for France.
Edit:
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.
That's very true. Cold weather really kills batteries that are left idle for even a few weeks and I don't think the 172 charges very well on the ground either at 1200 rpm.