Hi Macky and welcome to these boards.
I can't answer your question from our own experiences but I know from motorhomers web sites, particularly the continental ones that sking is a popular pastime with motorhomers.
To help with your search can I suggest my favourite campsite finder The Guide Bel-Air in paper form but www.francecamping.com
on the www.
The website can be searched in many ways, geographical etc. but for your purpose try inserting the word 'caravaneige' in the search box. This will provide a list 453 sites near to winter sports.
Clicking on a particular campsite name takes you to more information for that particular spot.
To refine it further you can use the list along the top of the main list.
Try clicking on 'site web' and this will give 10 sites which have a website for further information.
Maybe of some use to you away from the slopes.
Click on Geographique
Click on France
Insert 'permanent' in the search box and the list produced will be of French campsites open all year.
I hope this helps. Have fun.
(who much prefers to be tucked up warm at home if there's snow about.)