Survived the first night
Went up the hill last night to test drive my new sleeping bag in a "worst case scenario". So I took the sleeping bag, some warm clothes, a flask of tea and a blanket and went off to look for a patch of flat ground to sleep on. Having walked up hill for about 20 minutes I found a flat patch of snow, lay the blanket on it, put the sleeping bag on that and went to bed. Sure enough my body heat melted the snow which soaked the matress and then the sleeping bag so that kept me awake a bit, as did the snow falling on my face. However, I slept much better then imagined and got up feeling refreshed and keen to get on with the day, well keen to go home and have a shower and some scrambled eggs.
Conclusion, with some form of insulating layer to protect me from loosing body heat to the ground and something waterproof living in the snow in the alps in the winter should be possible.
Next step - get more kit and start building a shelter out of snow.