@sally1996 Are you sure it's damp/mould? A surveyor should be able to tell you that very easily as they have a little machine they hold up to the walls to detect it. Unless it smells really badly of damp, you can't tell from peeling wallpaper.
I bought an old house under asking because no one can else bid on it. The decor was so dated, wallpaper was peeling (there was wallpaper even on the ceiling) and there was staining that looked like damp. The surveyor confirmed there was zero damp, the staining was from the old gas fire (when we took out), as did the guy who removed the wallpaper and replastered the walls. Once the carpet was pulled up, new floorboards down and walls painted, the house looked completely different.
I wouldn't buy a house with damp. Go sale agreed, then pay for a survey which is not expensive in the grand scheme of buying a house (approx €500). Tell them you are specifically concerned about damp so ask them to check everywhere. If there is damp you can pull out of the same for that reason and get your full booking deposit back before contracts signed.