Like you, I have just been told by my vet that Nell has an under shot jaw. While this doesn't bother me too much - I hadn't intended to breed from her, or show her, I was told that she was from excently stock and came from show champion lines - and even though the vet said it isn't likely to trouble her too much - I am not entirely happy with the breeder and the ethics.
Having owned cockers for years, purely as members of the family, and having taken all the excellent advice from COL, I made sure I did all the research needed and checked out the breeder's credentials, to ensure that everything was above and beyond reproach. I even contacted and spoke to some members of COL, who had got puppies from the breeder.
The thing that annoys me is that I wasn't told about the undershot jaw by the breeder - who I would assume would have known about this, what with being a experienced breeder and all the knowledge gained from the years of showing and breeding. If they didn't spot it surely their vets would have, when she had her inital check, which I was informed was the case.
further to this, I paid a lot of money - £600, even though I had found other breeders selling cockers a lot cheaper, I wanted to avoid the horrors that I had read about on COL. Basically, This has left a bad taste in my mouth, especially, when I informed the breeder of Nell's undershot jaw, all they said was, bring her back and we'll refund you your money, or you can choose another puppy. Nell is not a pair of shoes!
I know I'm making a mountain out of a mole hill, and in all honesty, I couldn't be happier with Little Nell, and wouldn't change her for the world, but it really is a matter of principal. i really feel let down by the breeder and that I should have been told...Simple as that. Especially, after they had sold her on all the good points, rather than simply being honest. IK still would have taken her home!