Raywood said:
You can get covers for the vents which should help assuming the problem is when it is cold but they need to be taken off when it is hot or one off at others. We did have the problem in our last caravan at the bottom of the kitchen unit where wires and pipes came into the seat base and there was no problem in blocking the hole round these.
A previous caravan had a draught along the top of the fridge but that also could be sealed. What you must not do is block the external vents as Damian says but I see no problem with any gaps around the fridge that let cold air into the living area.
Firstly please note all that I said "temporarily" covering the drop vent under the cooker as part of trying to find out where the draught is coming in.
As for your last line above, may not see anything wrong with it but I would rather stay warm at night. We were in Somerset a couple of weeks ago and despite some warm clear days, at night we often got close to freezing outside - indeed our water froze up twice (serviced pitch,) we had several air frosts, and one small lot of snow. When the wind blows from the N or NE as it was then (caravan facing west) the heater just cannot keep up with the gale coming at it from the fridge area and we wake up at less than 10C inside the 'van.
All I want to know is the source/inlet of that internal gale.