The rule of thum is that you usually get better service from the smaller franchised dealers than the large groups, as staff are usually retained longer and have an ehtos, many of the large dealer groups rotate managers regulary while everytime you go in all the sales people have changed.
I used to work for a small independent franchised dealer many moons ago and can state that in general the customer service was outstanding in all aspects, it was quite a shock to the system when as a customer I started to have interactions with other delaerships.
I had such a appaling customer service from all the V/X dealership in my area of the NE that I ended up taking the vehicle to a smaller independant dealership up towards the borders an hr away.
Your not even guaranteed good service from the premium brands have experienced terrible service from Alfa.Merc and BMW dealers whicle I have had excellent service from Citroen, MG and Fiat delears the factor in all was that the good service was provided by smaller dealer groups and the bad was nearly always from the larger delear groups and I can only see the situation getting worse.