"A customer takes his vehicle to a main dealer which after all is the company that built the car in the first place". That is generally not true. Most manufacturers do not own any dealers in the UK. Yes, there is the Ford Retail Group, but they are 'just a handful'. Most dealers are companies who represent the manufacturer, and they can be 'sacked', after a period of notice.

I wonder, if in this case, if the car was much older than usual, in the Dealership? Was the job given to a relatively in-experienced operative? Was the Dealership of such a size that (real)customer care is placed well below sales targets?

Might we ever know the original fault codes?