Hi, thanks for the quick responses. The house is timber built with two blockwork end walls which have been harled. The structure seems to be (!) From inside.. plasterboard fixed to 4inch stud which has then been sheathed I think with ply. This has then got battens, not sure how thick, to which some OSB has been added. Then building paper and the cladding has been put straight onto the OSB. You may see from photos that the boards are coming off in places and paper is disintegrating. My thinking is to take it back to the ply, add new battens with some more insulation then paper batten and clad. For some reason I'm having trouble putting a photo on from my phone so I'll try another route!