Hi Heather,
How many people are sleeping in your caravan? If you are sleeping with all the windows shut and no heat on, as the temperature drops you will get condensation. We do a lot of winter caravanning and never experience condensation even when the outside temp drops well below freezing. The secret is to allow warm air to circulate round your caravan. No matter what the outside temp is we always leave one side window at the front and one side window at the rear on the night catch and leave the heating on low all night. Also leave your sunroof on the night catch or fanlight slightly open.
If you go out in the daytime, unless it is a warm day, leave your heating on low. This will prevent cold damp air from building up in your caravan.
When people breath they give out a lot of damp air, if breath comes into contact with the cold sides of a caravan you will get condensation.
If you follow the above you will have warm comfortable nights without the dreaded condensation.
Hamer