Thanks Jock1e. It does start in safe mode and remain there no problems. But nothing comes to light in there. In cannot find any conflicts (well nothing that sticks out and says here I am). I think I shall just try again this time with the media disk. Perhaps trying to install windows 8 from the image on my desktop might not have been the best idea of 2013.
Sony Xperia Z5 review: Hands-on with the phone which the Z3+ should have been