Just about to re-wallpaper a wall that until recently, formed part of a built in cupboard in the bedroom. The corner of this wall was a little damp with some mildew (mould?). I think I've rectified the source of the damp (cracked render outside) but I guess I need to treat the wall inside before I wallpaper. Any suggestions as to what in use to kill off any mildew and stop the stain from coming through the wallpaper? Many thanks.