Put a deposit on a puppy...

So I visited a kennel club accredited breeder and put a sizeable deposit on a cute puppy. Then the parents of the puppies came running over, and when I inspected them closely omg they were filthy and matted, and the female looked like it was blind in one eye, plus to my eyes they looked sort of deformed skeletally. So I was thinking omg, I just paid a deposit on a puppy from these freakish dogs, and I didn't know what to say, so I just left in shock.

On the way home I was thinking, there's no way I'm prepared to take on a puppy from those parents, they clearly aren't being looked after and god knows how the puppies will turn out when they grow up, because the parents are pedigree dogs but they didn't appear in good health. So I phoned the breeder an hour later and said look, I changed my mind about the puppy, can I have my deposit back? And she said no.

So now I'm kind of annoyed, cos she is keeping my deposit and still selling that dog for full price to someone else. It's not like she held the dog for me for any length of time or turned away other buyers - I paid the deposit at 9pm, and at 10pm I called and asked to cancel. But she didn't ask me to sign anything, and she never said the deposit was non-refundable when I paid it. Should I be entitled to a cooling-off period in which to ask for my deposit to be refunded? Or can I ask for it back because she didn't say it was non-refundable?

I really don't want to lose my deposit cos I can't afford it, but at the same time I can't take on a puppy from those freakish looking filthy parents - all puppies are cute, but god knows what sort of problems they will have when they grow up, what vet treatments they'll need if they go part blind like their mum appeared to be. I guess I should have examined the parents before I paid anything, but I don't know much about buying dogs. Is there anything I can do? Help!

What happened?