Hi,
I have looked into this previously and have found the best results by googling caravanneige, which basically means, caravanning in the winter, France comes up as a favourite ( Grand bornand) although there are sites in Austria, which are seriously geared up for winter sports, with the lifts climbing straight over the campsites, on one website.
The Germans apparently are big into wintersports and caravans.
From a monetary exercise thought, depending on how many of you will be going, the package deal will take some beating ( free child spaces) followed by the self drive and the self catering with apartment rental, there's so much choice, so as much as I enjoy caravanning the potential of -17 overnight in a caravan (January-Febuary) doesn't sound appealing. Although skiing in france this year, (middle of March) was similiar to a British summers day, with a group of French students skiing in their underpants! it was that warm. If your a seasoned skier, then I haven't told you anything new, but I would be interested in how you get on.
So basically pick the date carefully, I also seem to remember that it is popular with Motorcaravans, who tend to have their own section to the carpark, I didn't see any electrical hookups though? or caravans, so I would imagine that it will need to be the caravan site.
Regards Paul.