Well a pair of them turned up to do this. We had a good chat about the forum collective wisdom and it was his view that we should try it with the old seal and no sealant first. I measured the old screen (that was in with no sealant whatsoever and did not leak a drop) and it was between 4.8 and 5mm. The new screen measure around 5.5mm so not thinner. It certainly fought him every step of the way. It did not want to go in. Pretty tight. I have to say that I was confident as he was that it wouldn't leak being that tight. He did say if it leaked, he'd rather come back and seal it than do that now.
There was a quite large hole in the top of the screen going through into the roof I guess. Outside the pinch seal, but a damn hole nonetheless. I cleaned it up and filled it whilst they waited. How good a repair? Well it's not a hole anymore so that's better.
I was on the phone when they were leaving so couldn't try the screen until later. I gave it a significant hosing, blasting the seal all round. I waited for a while and yes, there was very slight evidence of droplets in the corner of the screen above the dash, so obviously I'll have them back. But I might just drive a bout a bit first and see if the screen will wiggle in a bit and seal. It's undergone major trauma getting it in. I doubt that will do it, but I'll give it a whirl until they return. The fitters were good lads and pretty experienced, but as for AW themselves, poor in all respects really. It's a shame about the leak, it's pretty small, but I did want to give it a go. Not a great surprise but it adds to the bank of knowledge. I think it will surprise him that it leaks at all.