Moisture/Damp around Boiler

Hi All

My boiler in the house is in the upstairs back bedroom (2 bed terrace) and since coming back from a few week holiday I noticed the wallpaper on the wall in the dining room directly beneath was bubbling and damp. When I went upstairs the wallpaper around the boiler was damp too, and even a tiny bit of mould on the far side. so far I haven't been able to find any source of leak except potentially the flue thats going out the side of the house from the boiler, it appears to be at a slight upward angle so water is dripping back down the underside of the pipe to the exterior wall however that wouldn't explain the damp all around the boiler where even if that flow was coming back in through the wall, wouldn't effect it.

I've recently bought the house and am in the process of doing it up so that wallpaper was going anyway but now wondering whether I should get a plumber in the check it out or whether this is simply down to me having left the boiler plugged in (although not on) while I was away? Anyone knowledgeable about boilers seen this before?

Thanks in advance

This seems a very similar situation to what's happening with my pipe, must check the pressure when I get home

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Damp wall around a boiler spells trouble get a Registered Gas Engineer to give it a once over - especially as you have just bought the house, you will have no idea on the condition or safety of the boiler and it is in a bedroom!! enough said I think