I had work done on the loft and had inward opening UPVC double doors
fitted instead of a window.   As with most conversions, the wall is
stud with waterproof membrane fitted underneath roof tiles as the
outer surface.  Between the ends of the tiles and the frame has been
filled with mortar.

A few queries if I may:-

1.  How far should the outside upvc sill fit behind the tiles and
under the mortar?

2. Should there have also been a sealant like silicon, at least at the
juncture of the sill and the mortar?

3. Should the rubber membrane between the door and frame be enough to
make a waterproof seal against rain flowing down the door?  

TIA