Maybe a stupid question, but you have checked that the extractor vent from the bathroom does actually connect to the outside? The reason I ask is because when we bought a new build a good few years ago, we had condensation in the loft and we found the pipe connecting extractor to installed soffit vent wasn't actually connected at both ends and was underneath the insulation that had been laid on top. Reconnected, and the problem went away....
I was there yesterday & Noticed these in the Loft, I assume that one of these is the Extractor Fan, so was wondering what the 2nd Pipe is?? That seems to just stop in Mid-Air....??