Hi Clair,
We have taken the van skiing in the past but you really need to be geared up for it. You didn't mention whether you plan to go abroad or to Scotland but the principal is the same except overnight temperatures are generally a lot colder in the Alps.
If you want guaranteed snow you had better go abroad. Remember that snow chains are compulsary in the Alps even with a 4x4.
I installed an extra water point under the toilet sink so that the Aquaroll could be set up in the shower tray to prevent freezing. The external point is then plugged off. I also added some anti freeze to the toilet flush. You need to change your gas system to propane and may need an insulated cover for the gas bottle if it gets really cold.
The biggest problem is getting ski jackets, trousers, gloves etc dried. Some sites in the Alps have drying rooms but generally sites in Scotland don't. If you clear out all the unecessary gear from your caravan you can dry boots and gloves in the external lockers providing that the blown air system has vents in these lockers - mine does. Jackets can be hung in the toilet if dripping wet otherwise just hang in the wardrobe and the heat from the Carver heater will dry them. We kept the wardrobe for outdoor clothes only and put shirts etc in the overhead lockers so as not to pick up damp off the jackets. We used to leave our electric heater on 24 hrs a day as the van really will freeze up fast without it.
If you can do all of the above it's really no problem and great fun. There is a good site at Bourg Saint Maurice in France which gives you access to Les Arcs and La Plagne ski areas.
In Scotland the CC site "Invercauld" is within easy driving distance from both Glenshee and the Lecht ski centers. Also Glenmore Caravan Park is situated below the Cairgorm ski center.
If needed you can hire skis from all these areas.