Reading through the Focus MOT thread reminds me of a case of unauthorised work by a dealer a few years ago on my Focus.
I had taken my Focus into a local main Ford dealer for a standard service. We had agreed a fixed price in advance (they price matched another local dealer) and I dropped off my car in the morning. I was out and about all day so I left my mobile number.
At the end of the day I went to collect the car. The receptionist was preparing the invoice and she asked "someone did phone you about the anti roll bar link rod"? I replied that they hadn't. She looked worried and went away for a few minutes. When she came back she said that they had found a worn anti roll bar link on the O/S and that someone was supposed to have phoned for authorisation to change it but she admitted that this never happened and they had changed it anyway. She said that this was their fault and that they wouldn't bill me for it.
Now I knew that the link rod was shagged. It was a common fault on early Focus models and I had replaced the N/S on the previous year. The O/S one had been clonking for months but I hadn't got round to replacing it. I told the receptionist that I knew that it had been knackered and that I had intended to replace it myself. I told her that I was prepared to pay for the part but not the labour. She was so pleased that I had volunteered to pay for the part and she discounted the part down to trade prices.
I was happy because the link rod got changed for less than I could have done it and without me getting grubby. She was happy because the dealer got some cash back for their c*ck-up.