Thanks for your answer. I could not remember which web site I placed the question and it has taken me ages to find it. Now added to favourites.
The walls dry out if we open the windows on a sunny day but once we close the windows the damp starts to come back again. Anyone got any bright ideas. We were thinking that the damp may have become trapped within the plaster and that we need to remove the plaster and let the walls dry out completely. The flashing has definitely worked. The outside is rendered but that looks ok.
Damp problem.
May 2009