Did you ask them at Autobahn how much they'd do it for? They did a helluva job on my car. To make it even better, I called two install shops "after the fact" just to see if I could have saved any major dollars and found out I'd actually gotten about the best price of all three at the dealer.
Although our buddy Don started to try and do the sales job on me to get the film when I purchased the car, I already knew I was going to do it so it was an easy sell for him. Might give them a call. A little surprising that they didn't try and sell this to you when you bought the car.
'05 330i ZHP in Imola