Approx 3 months ago now we stripped this wall and skimmed it (a DIY job...regrets). It originally had horrible thick textured polystyrene wallpaper over it. There were mould patches under the wallpaper but we assumed this was related to condensation. Since skimming, there have been these small round wet patches coming and going (worse when it rains). The two larger patches have been there since the start and have never dried, that may even have grown Assumed they were stains or would eventually dry but now realising otherwise. The wall is one side of my sort-of conservatory with axiome type plastic roof, at the back of the house. It's a victorian terrace but I'm not sure when the conservatory area was built. On the other side of the wall is the neighbours' kitchen which was a 1980s extension apparently. I've noticed some of the flashing on the conservatory roof isn't flat, so thinking this could be leading to some sort of leak behind the plaster? Though the wet patches aren't necessarily concentrated below that area. Basically just hoping for someone to tell me that it's not going to be a massive job to fix that requires taking the plaster back to brick I don't even know what kind of tradesperson would be best to help with this. https://ibb.co/sHg4vSt https://ibb.co/gmtx8qq https://ibb.co/r22FBVq https://ibb.co/YTMCMYy https://ibb.co/bHgd6VZ
I'd dig at the damp spots back to brick to see if it's damp if you can identify any other problems that can cause this issue