You can get mould on any cold walls because there is water vapour in the air from our bodies, etc and above a certain partial pressure it will condense on the cooler spots in the room, giving a nice wet environment for mould (and insects, like woodlice) to thrive in. Just move your chest of drawers to an inside wall. It is keeping the wall cold and thereby encouraging condensation. Not only that, it is stopping water vapour from blowing away and hence hindering evaporation. You want the water in your room to be in vapour form, not liquid. Only well insulated or south-facing outside walls can cope with a piece of furniture against them. If you really want to keep the chest in the same position, line the wall with thin insulation sheet. As long as water vapour can't get behind the sheet and condense there then you should be all right after that. Look askance at "damp proofing" firms. You usually don't need any of that. The houses were probably OK when they were built, even 100 years ago. Before you go down that route, have a look outside and make sure your damp course (probably hard bricks or slate for you) has not been circumvented by a raised path, raised earth or rubbish. Only "damp proofing" firms bent on self destruction will inform you of that. None of the wall bricks above the damp course should have contact with the ground by any route except via a damp course. Of course, an easier but probably impracticable solution would be to not heat the room and to never go into it.