Make note:
Quality is quality. Quality is a standard of work.
Reguardless of whether I change a tail light , or whether I rebuild a starter. I will always give the same quality to my work.
Reguardless of how much one job cost compared to the other. I will still perform my same quality of workmanship. Reguardless on whether I think the car is a ####box. Its the customers car. I will still perform my same quality of work standard.
Quality in my case has no reflection on customers stupidity.
Like I said in my original post. I will perform the work I quote.
Dodgeman your ignorance to me is proving to make you blind to what I have actaully written. I have never once said my quality of service will change, no matter how much you try to make it appear as though I am saying it will.
If you agree to work to be carried out, thats your decision. My quality of work will remain the same no matter the job performed.

If I conduct work without the customers approval first. Then yes that is wrong And as a customer, The Dept of Fair Trading will allow you to remove your car from my workshop without paying for the un agreed work, as a result of my stupidity.