I live in a converted warehouse with very old exposed brickwork inside. For a while I have started to smell mould on one side of the room. I have just lifted a poster to find lots of white fluffy mould underneath. Now that I look closer there is a very thin layer of white over most of the wall. And a lot of the brick is crumbling off, which I have read is efflorescence? But I'm sure that some of what I'm seeing is mould. What is the best way to treat this situation? And importantly prevent it from returning. Will it help once we turn the central heating on?