Conor ( snipped-for-privacy@gmail.com) gurgled happily, sounding much like they were saying :
If there's going to be much of a cost difference from the original quote, then ringing the customer and saying "Look, we've taken the car apart to get to that pipe - and there's others that are fooked, too. Total should be about £170. No, there isn't really a choice. See you later." really isn't too onerous, and is basic good manners and business sense.
Which is probably why many garages don't bother.