I belive that most of the experts on here reckon that only one in a hundred need changing now!
I think the high fail rate (in the past) probably has more to do with fast fit clutch centers profit margins than reality!!
If they see you bring in a car worth circa £800-1200 they realise that your likely to not bother with doing it at all if the quotes to high so they are quoteing the costs more sensibly rather than lose the work!
Andy