The car was back to the dealers and after having the car for a full day and taking it for 4 test drives, they couldn't find a fault. I took one of their technician's out and managed to replicate it, as it happened 99 times out of a 100 when pulling onto my drive. To be fair to them, I did have difficulty replicating it but that's typical when you're trying to demonstrate a fault! Agreed it must be either top mount or shock absorber, and they kept the car for the following two days and replaced the top mount first. It now seems to be much better, and I must say in fairness to the dealers I didn't have any issues with them. The knock was evident again last night though, when navigating a new housing estate with particularly large speed bumps (full width of the road). Does anyone get anything similar on a car with DCC and 19s?