The breeder has to have the puppies microchipped before they go to their new homes, it's now required by law. Have a read of this microchipping factsheet. Are the puppies docked? If they are then the following paragraph about exemptions will be relevant:
The first exemption is where a veterinarian has certified the dog as a working dog and docked its tail in accordance with the Animal Welfare Act 2006. In such cases the time limit for the dog to be microchipped and details recorded with a database is extended to 12 weeks. The dog can be passed on to a new keeper once it has been microchipped.
Both parents should have had a BVA eye test, a BVA gonioscopy and have had their hips scored. A hip score is presented as a single number which is the result of adding the score for each hip together. The overall score for each dog should be well under the breed mean score (13 for cockers, 14 for springers) and the two numbers should be fairly even, i.e. you don't want one hip with a considerably higher score than the other even if the overall score is lower than the breed mean.
There are differing DNA tests for each breed which should also have been done. Even if it's not possible to produce affected puppies when crossing differing breeds it's still important to know whether any of the pups could be carriers for anything. The cocker parent should have had DNA tests for progressive retinal atrophy (prcd-PRA), familial nephropathy and acral mutilation syndrome. The springer parent should have had DNA tests for PRA, fucosidosis and phosphofructokinase deficiency.
The breeder should have official paperwork for all these and be happy to show them to you. Alternatively if both parents are registered with the KC and you know their full names you can check their health test results here on the KC site.
As previous posters have said the breeder should have thoroughly grilled you. I'd expect them to have asked about your home and lifestyle, what you feel you can offer a dog, why you picked that breed/cross, why you picked that particular litter, what it is you want from a dog, what (if anything) you want to do with them in the future sport/competition/working wise.
This Champdogs article about buying a puppy is a good read, as is their list of questions to ask a breeder.