After spending a year in time and much money I have at last stopped the water leak from my screen.
I have had the sunroofs removed and re seated and the screen removed by Autoglass 3 times and then twice more by other windscreen firms none of which managed to stop the leak.
The leak manifested itself in the right hand top corner of the roof lining and when I braked or went round a bend I ended up with a wet lap.
In the end I purchased a cartridge of auto silicone sealer removed the front driver-side finisher and rammed the nozzle right up into the corner under the rubber then went right along the top finisher between the roof and the rubber .
Much to my surprise no more leak. If I had done this in the first place I would have saved myself a good deal of money.