@bobasd I've checked on the external and there are no signs of any damp coming through whatsoever (see photos - area in red box). I've checked the wall in the loft and no issues there. Somebody mentioned above about builders dirt. Well the loft is full of masonry dust - so could this be the...
There is no sign of any water leak from the loft above (and don't have a F&E tank any more - long gone replaced by a Combi) and I'm pretty sure its not condensation based. Any remedies?
On my upstairs back room there are these brown stains/blotches on the wallpaper. These are on the exterior wall. I've checked the brick work on the outside for the sign of any penetrative damp, but there are no signs. The blotches are mainly located on the top of the wall, as in the image, but...