I purchased a new build property 4 years ago and ever since I've had problems with leaks both inside and outside down from the front wall. I've complained to the developer countless times and had some work completed such as the sealing of the rooflights but still I'm plagued with leakage. Without going to a lawyer with enough proof I'm a little stuck! To make matters worse even NHBC wouldn't insure it!
The property is very different in that the roof is a curved metal sheeting with two Velux roof lights.
There is no loft or attic and no space between the roof and ceiling. I have my suspections that there is no waterproof membrane between the ceiling and metal sheeting, basically when I took out a ceiling light fitting I could touch the underside of the metal roof!
My main question is, should the developer had used a waterproof membrane or something similar that would provide an extra layer of protection by law?
From your last picture it looks to me as though the velux windows have not been fitted correctly - there should be a flashing down the side of the windows which laps onto the tin roof material.
Can only suggest you get hold of velux and see if they have a site survey team.