Re: GT black/metallic black ?
Shame you didn't buy one earlier, then you could have had one in Brunello Red, which despite my usual dislike of red cars, looks wonderful, so much so that I bought one! Sadly though the colour was withdrawn as being too expensive to manufacture- apparently!!!!!
As for parking sensors, they really are a must, the car is almost impossible to reverse without them, and as Fred says, they would be very useful on the front as well.
Anyway, I'm sure you will love the car no matter what you order.