Thanks very much :) On further exploration we have found more damp marks in a wall press in an adjacent room but its not the same wall. Its a bit dark to get exterior pictures at the moment so I'll try to get them tomorrow but I've added two pictures of the wall press and one of the airing...
I was wondering if anyone could advise on the best course of action (and estimates of costs involved) with a leak we have just noticed.
We moved into a new house about 6 months ago, and haven't had any problems up until the last week when we noticed a large brown water stain in our airing...