guys, many thanks for all your replies.I do , however, need to , or at least attempt to, quantify the extent of the damp problem. There is no mould, no `hollow`plaster and no wallpaper peeling down the walls. This is a relatively small area of loose wallpaper pf about 3 x 3 feet of absolute maximum, either side of an outside corner just above the skirting board. It's about 2 feet above the pathway around the edge of the garden and after checking the outside rendered and professionally painted wall i can see absolutely no evidence of where water may be seeping through. The only place that i can imagine where the source lies is either where the path meets the wall ,and i can see a gap, in fact i've had to kill weeds there, or it's perhaps coming from an outside drain which is at the problem corner, but remember it's manifesting about 2 feet above drain and the gap so are they really possible sources?.