Regarding cavity wall insulation: as it turns out, what we believe was sagged wool insulation turned out to be just a sloppy job. Ground floor walls are still mostly full and not moist, first floor is mostly empty. They basically did not the first floor at all. The company who attended said maybe it was done as part of a government funded initiative to insulated council blocks and so the installers had way too many jobs to do in a day to care about insulating it properly.