I have the kit (from Oz so slightly at the slightly higher price paid by Steve) but haven't managed to arrange fitting, partly due to my commitments, and partly finding a day that Prestige can come down to South London. They don't have premises, unfortunately, so offering to travel up didn't help. Am exploring local fitters as well... If I have any luck, I'll post feedback.
Update: the stars aligned on Monday, and I managed to get this fitted, at home on the drive, by Prestige.
So far, so good. I'm running Android Auto and it's pretty slick. Installation was neat and good value, especially for the convenience factor.
I'd say my only slight disappointments are:
1. Visually: reflectiveness of the touchscreen.
2. Tactility: I can feel it is an overlay, in that there is a very slight movement when pressed before it presses against the original screen behind. Makes it a little hard to swipe, but the scrollbar on the left works perfectly.
3. Audibly: It sounds great (well, as good as the original system allows) but the microphone pickup for "Hey Google" is not great. Voice control once I'm past that point is good, but it struggles to pick out the keywords against background noise I guess. A quick press on the microphone on screen shortcuts this.
But given main objectives were decent navigation, wider range of music options (streaming etc) and a more user friendly package than stock, I think it was worth it.