the audi dealer agreed to replace the rear windscreen with shows a visibility problem at the upper end , the new windscreen fitted is no better and i have seen this problem on other similar A8L any ideas??????????????

Perhaps you've already tried this and hope you have but here is the obvious...Could you possibly adjust your seat to help the angle and thus the view. I've experienced no problems with screen visibility and normally have it in the "up" position all the times.

when you look back in the window, in the upper part, you have a blue part, sort of stripe, and between the blue and the normal part, i think you see some distorsion of the image... dont you?