Although the idea of using the van in winter has attractions the difficulties I feel are the fact that up here in the north, daylight disappears rapidly. Having lived in the north east for a long time I am aware that it will only get light around 9.30 am and will be dark again at 3 pm, so not a long day to do anything. Having looked at the storage site where I keep my van it appears there are about 250 other users who think like me that winter is a time for consideration of adventures to be taken in Spring. So how to protect your van?
Obviously remove all water, so drain everything and leave the taps open. Grease the flap of the cassette toilet with olive oil, not vaseline. Remove, if you can, all the cushions and bedding to a dry place at home. Remove gas cylinders, if you can to the garage. Remove all food, as mice will enjoy anything you leave. A breatheable cover is a good idea, but ensure the van is clean and dry before you put it on. Leave the handbrake off and at least once per month revolve the wheels. This may mean jacking up the van. Of course take security precautions by fixing a clamp and hitchlock as a minimum. Remove any leisure battery and keep topped up with regular charges in the garage.
Apart from that, not too much. Just keep an eye on it during the winter to ensure that if anything does go amiss, you know about it quickly and can stop a small problem becoming a big one.
Buy a bottle of whisky and start reading about sites you may wish to visit in the Spring. Alternatively, head to the south of Spain and enjoy the mild weather.