If you talk to customer services, there is normally a half decent person on the other end of the phone.
Already done that..........there was just somebody who would not pass comment, played the political line and took the details.!
My experience with high profile companies that do shoddy work is that they handle complaints very well. I believe they aim to get away with doing half a job because 95% of customers don't know a good job from a bad one and therefore go away happy. The 5% who complain they can afford to treat very well to avoid getting a bad name.
My guess is that you'll get phoned by an area customer relations guy who will argree with everything you complain about, resolve the situation and promise to give the cowboys involved a b0110ck1ng, which he won't, of course.
Hope it gets sorted anyway. It's frustrating when you maintain your own car and the one or two things you entrust to others get botched.
Kevin