Thanks for the advice everyone.
Dissapointingly dealer was no help when it came to the Q5- no information.
Don't need extra performance of a 4.2TDI nor S8 as I have a 911 already, just needed a family car.
Had a test drive in the A8, frankly it was fine but not special. Felt to me like a bigger version of an A4, and I do agree about the gearbox as well.
The nail in the coffin was the attitude of Audi dealer, killed the deal- BMW offered a finance deal at 125GBP a month less than Audi and also offered 2.5k more for my P/X for either a 535d M sport or 730d Sport priced the same as the Audi A8.
Audi obviously don't need the business!!
Also thought about a S class but it's a bit too big so I am looking at CLS's as well...