I agree with Pete and Pete.
My VW van is well out of warranty so I use a local garage who are specialists in commercials and I can trust to do an excellent job at a decent rate. The owner has become a friend over the years.
However our cars are different. Wife is on her 3rd Mini which have always had the TLC package which includes servicing for 5 years and my last 2 BMWs have been serviced by the main dealer as will be my Audi.
What I did do was contact the 2 Newcastle companies who specialise in servicing of German cars to get quotes which I then used to squeeze the dealer. Last service I saved £60 so if they want the business they'll negotiate to a point. They also want to sell you your next car so I play on that.
Whilst the manufacturers must honour the warranty whoever does the servicing providing they are VAT registered and used genuine parts, they are much less accommodating when things go wrong.
I have 2 examples where the dealers have hooked up cars directly to the manufacturers engineers, (It's weird to see a car in a workshop and watch a series of tests, lights , engine start stop etc. being carried out remotely from hundreds of miles away :shock: ).
My wifes current mini cooper was intermittently dropping the bluetooth connection to her iphone. Not major issues and difficult to sort, they had the car in for a week, loaned her a new 4x4 countryman, updated all the software and put in a new multi media unit not giving up until it was fully sorted.
I felt the clutch on my BMW had a very slight shudder occasionally so a week before it's 3rd birthday I put it in to the dealer for its 1st MOT and asked them to check it at the same time. They loaned me a car and hooked mine up to BMW UK who sanctioned replacement of some engine turbo parts which were slightly out of tollerance (not related to the problem) as well as updating the software. They also fitted a new clutch and flywheel. All under warranty and less than a week before it's expiry. I doubt that would have happened had I not kept goodwill with the main dealer servicing.
Bob