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I do use a dehumidifier in there and keep the room warm,
Yes we do have Cavity Walls that were treated 3 years ago. The damp/condensation were there before and since so filling them seems to have done nothing to help.
When you suggest warming the exterior wall, how do you mean please? Is there something we can have coated on the wall, such as a special paper? There is no chance to turn the room round so the bed head is on another wall, they simply aren't big enough. By the way its a ground floor apartment.
Thanks for your help all.