Well the plot thickens.
They have contacted me today to inform me that the removal, cleaning and re bonding of the screen went well and no breakages. It has all been leak tested and dried out and trim refitted, so sorted.
But then he tells me that the screen has been removed and refitted at some point in the past !!

The car's only 6 years old and I've had it for 3 of those, so I need to find out a bit more there.
It's the original Audi tinted privacy screen so doubt it's been replaced by someone like AutoGlass, so will ask the dealer if they knew of any work done by themselves. The car was owned/used by director of that dealership for a year and then owned by a local person who would have taken it to that same dealer for any work for sure and it would have still been under warranty anyway. Bit odd but never mind. I will get some more information from them tomorrow and see what they can find out.
That was the reason for my leak anyway. Poor fitment or poor adhesive or both. Hopefully now it will be sorted for years to come and no more condensation or leaks.