I can't help much except to say that the sales side of Amersham is dire compared to Aylesbury. When I arrived at Amersham for a pre booked test drive, they told me the car wasn't there as somebody had gone sick. I asked why they hadn't rung me and they just shrugged.
Aylesbury on the other hand were anything but pushy, never chased me and I tested 3 different cars there. They also gave me nearly £2000 of the list price, which was £700 better than Milton Keynes or West London.
Any dealer would understandably put there own customers before an import, but I'm not sure this would be to much of an issue.
My car broke down on the day of delivery and Aylesbury took 4 days to fix it. Its now broken down again (well, it is a month old now) and they are going to collect it next week.
No problems with the dealer - just the car.