No heating in my van and I'm spending more time in it than at home because I can't afford to heat the house and it's warmer in the van than the house. As Kimbo says, you do acclimatize and I wear wool clothes, have wool blankets and am never cold in bed. Also wearing a hat in bed makes a big difference.
The long evenings can be hard but I try to keep busy and active, walk the dogs, eat later about 8pm so that warms up the van and then washing up etc occupies me for another hour or so.
A few candles in hanging lanterns helps and when really cold I light the gas cooker for an hour or so, boiling water for a big flask at the same time.
Double lined curtains, draught excluder, an old blanket on the floor, bio ethanol heater, woolly jumpers, thermal undies, 2 dogs (which apparently generate half a kw of heat each) to snuggle up with, candles, and a pan of milk on the stove for a hot chocolate all make a difference. Plus hot water bottles, hot rocks and extra insulation stuffed in every crack too.
In the morning I run the engine for 15 mins to warm up and get rid of condensation. I find the damp harder to cope with than the cold especially after several days of rain.
If moving on I try to wait until it's dark so that occupies me in the dark hours and means that the van is warm on arrival and battening down the hatches means keeping the heat in for as long as possible.
And best of all, park up somewhere isolated and light a campfire which keeps you busy and warm.
Try living at home without heating for a week and then the van will feel warm in comparison!
And eat lots of pasta, nuts and Christmas cake for extra calories.
