Thanks for your reply and advice, it sounds as thought this maybe an expensive problem to fix.
I have been told there should a sag in the sarking overlaps which would add to the airflow, in my case the overlaps are tight and it's been suggested that an inserts should installed at a number...
I've had condensation in the well insulated loft of my house each year since buying it new 12 years ago. This year it was very severe and resulted in extensive mould/mildew. The problem was investigated twice by NHBC surveyors during the 10 year guarantee period and on each occasion their...