Hi Peter.
Winter caravanning is realy not hard to do, you just have to think ahead and prepare for the worst, then anything else is better.
We are fulltimers, so having to cope with winter has been a priority for the last 3 years.
I use a scenic porch awning set up on the right hand side of the van to cover the aquaroll and waste carriers. This does keep frost at bay a treat. I also use a XXL sixe puffa jacket bought for a fiver from a charity shop to insulate the aquaroll, and I use the sleeve of the jacket to insulate the pump feed pipe from the barrel to the van. I use a cup full of cheap table salt added to the wastemaster to combat freezing there. Also a bottle of cheap vinegar can help. As a last resort some car anti freeze could be used.
I have made a stand for the aquaroll using a decking plank from B & Q to make a platform that is 10cm off the ground to stop the bottom of the barrel freezing.
We also keep a 10 litre can of water inside the van for hot drinks. This alone will normally last a weekend for drinks.
As Dusty has said, a shovel and broom come in handy for snow. I have found that the telescopic caravan hose brush is better for clearing the awning as it's longer than a broom. Don't be tempted to take the awning down even with a couple of inches of snow. We tried that last winter and it was bloomin heavy.
In the car you shouls have an emergencey kit.
Jump leads (to start the car off the caravan battery if stuck.It isn't ideal but does work.)
Tow rope
Shovel
A hand winch is handy to pull the van.
Fully charged mobile phone and car charger.
Hi Viz builders jacket (Very warm and bright so you can be seen)
Gloves & thermal hat
A couple of car blankets.
A torch (wind up one is best)
Hazard triangle
Basic first aid kit.
Wellingtons.
A windscreen cover and a couple of black bags to cover the front doors of the car. Slit them down one length to make a door sock. This helps to stop the door freezing shut.
There's probably more, but that should help you to enjoy winter.
If you can, tell a friend or relative of your travel plans and arrange a time to call them to say your safe. That way, if you're say more than an 2 hours late and you have not updated your contact, they can start to check your safety, firstly by ringing the site your going to, then if no success, the police to report the situation.
It might sound a bit ott, but if you get stuck miles from anywhere, you can be assured that someone will automatically initiate a search, even if your phone won't work and the car is stuck.
Most of all, keep a sense of humor. There's no point in getting annoyed at being stuck or things not working. Calmly "thinking outside the box", often brings a result.