The wardrobes badly need ventilation, nilrac. A 9" x 3" (225mm x 75mm) through the wall to outside, and the same in the ceiling of the wardrobe.
Cavity wall insulation would help against the mattress damp. A small vent in the bedroom ceiling wouldn't hurt, either.... or window trickle ventilation.
I fixed this very problem recently in an unheated bungalow, by fitting a very small storage heater on overnight tariff.
So, it's heating or ventilation, or best of all, both :o)))