I started a thread under the Ghibli section titled 'Euro 6', related to just this point.
My car is Euro 6 - Ghibli Diesel with Add blue, but registered in July 15. If I had reg my car on Sept 1 no problem. But the same car registered on 31 July due to an admin error with Maserati had been marked down as Euro 5.
Now I'm trying to get paperwork from Maserati to confirm the fact that it is Euro 6 as they have confirmed.
As I said on the other thread, there will be plenty of drivers who won't check and will end up paying the charges.
Rip off Britain alive and well!!