Anyone know the average VW paint thickness for the GTI

The reason I ask, is that I had my car professionally detailed last week and the thickness of the DBP paint/clearcoat on the roof is significantly less than that of all the other panels on the rest of the car (these are described as being totally consistent with VW standard paint quality). I don't have the actual figures yet as I'm awaiting email confirmation from the detailer.
By way of history, my car had to have the bonnet resprayed (twice) to correct a paint fault at delivery (basically some scrote pulled up the wiper arms prior to/during the PDI and took slivers of paint off the back edge of the bonnet - 2 cosmetic touch ups and 2 full bonnet resprays to correct - you do the maths - was the fault corrected the first, second, third or fourth time

).
Sadly, and even more unfortunately (why me, again), after the second full bonnet respray, some overspray or solvent

found it's way onto the roof and etched itself quite deeply into the clearcoat. It could not simply be removed by polishing and more aggressive mopping would seem to have been carried out. I was led to believe that the roof had been fully repainted, however the paint depth readings would seem to preclude that remedy. I've just emailed the dealer bodyshop and await their response. The last thing I want to do is put my newly detailed car back in their hands again but sadly I have to do that later this week as the aircon condensor/dryer/other is being replaced under warranty

I'll also be contacting VW Customer Services but want to be sure of my figures first.
Cass