we have a 5' area of damp at the top of the kitchen wall, its directly under
our bath and on the other side the neighbours bath. Im 100% sure our bath is
sealed and our pipes which are above the ceiling are ok as the plasterboard
is totally dry.

Do you guys reckon its possible the neighbours who are known for not
(maintaining their property )could have a bath thats not sealed and would
cause damp to penetrate the party wall? We have a couple of heating pipes
running vertically in the wall at about the same spot, but the combi heating
pressure has been fine, and the system was drained for most of the summer.
There is no cavity, the walls built of a double course of engineering bricks
circa 1934 about 12" thick.

The patch is about 5' diameter and its making the wallpaper peel. We first
noticed it about a year ago. Ive been round today but no one is about Ive no
doubt they will deny there is a problem.