Guys if you feel that you are being shafted - and most people know when things are out of hand - you need to go straight to the Office of Fair Trading website and lodge a dispute.
We like to think that we can have a conversation, agree a price, and get what we expect. Problem is that if it goes wrong it can go really wrong, and there needs to be some work done to avert that ie get written quotes particularly on the big $ stuff. Not trying to tell anyone how to suck eggs, and it's been said a thousand times before, but GET QUOTES. I've negotiated quotes at length to make sure the vendor knows what I expect and that I know what I am or aren't getting.
If a workshop does in fact try to take advantage they need to be hammered for it. Luckily I have not had a problem with anyone local.
Cheers