Well, I have found my local main dealer (Preston, Lancs) to be very receptive to price matching for repairs........and lets face it I do trust the work they do as they offer a better guarantee on their work than you will find any independent or other garage will offer (case in point my cambelt & water pump 2 years warranty - best I could get from anyone else doing it was 3 months - and by the way they price matched Stafford Audi so got the job done for about £450 instead of the original £650 I was quoted - I could of geot the job done at an independant garage for £400 but for the sake of £50 I though an Audi Main Dealer was a better bet).
However, in the case of Preston Audi, one has to ask why they have just built a big extention on their showroom.....which was big enough in the 1st place if you ask me - the business overheads on these gin palaces must be huge - ironically, last time I was in there one employee told me that they had to "let some people go" cos the bottom had fallen out of the car market !
I could do without all the flashy showrooms...and the Parts dept is buried amongst all this flashiness . I would far rather go to a storeroom and talk to the people looking after the parts direct.
Back to the original point though I have not yet been in the position where I have had to get a fault diagnosis done...and I have to say I would probably get an independant to do the diagnosis & repair......but it depends on how long you are going to hkeep the car I s'pose....you pays your money and makes your choices