Hello Mark,
Winter caravanning, if the conditions are likely to be freezing or below, then there is a need to protect your water barrel from freezing by lagging it, or using a winterisation kit, that allows you have a smaller water container kept inside the caravan - usully in the bathroom.
The other issue is using Butane gas. The bottles will reduce or stop producing gas if the temperature falls to around freezing. To overcome this, switch to Propane gas.
Other issues relate to freezing waste pipes. Make sure the waste pipes are clipped properly to the underside of the caravan and don't have any sagging sections that might retain water and then freeze.
If you have a water heater, make sure you keep it warm, other wise if water freezes in it, it will damage it.