I am very sorry for your situation 
Many things raise red flags for me I am afraid. All raised above.
I agree with mutty. Puppies learn how to be social, well adjusted dogs by having siblings. All that play fighting etc. that they do is teaching them valuable lessons for adulthood. So, you may not just have health issues, but social issues as well.
I know you might feel bad about letting a 'friend' down but you may well be saddled with huge vet bills and behaviour issues for the next 15 years. Do you really want that? Don't feel bad.
They have asked you for money anyway, and are still prepared to sell the remaining puppy, which says it all really.
And the fact that they have bred for the wrong reasons and have bred a cross breed, wrapped up in a designer name.
In other matters
are you aware how er, busy a springer/cocker cross would be? She says, with a Springer and a Cocker currently asleep at my feet. Mine are lovely, but need bags of exercise and stimulation in the form of training (you can't really wear them out physically). In reality, I am out for 2 hours a day, in mud, rain, wind, snow etc. My DC are teenagers, so can be left alone and even help with the walking and training, but they are not breeds that will be happy with a quick walk round the block.
Is there anything about either a Cocker or a Springer that would put you off having either? Why a Sprocker in particular?
Good luck OP. Carefully research your next breeder if you can 