Hi, sorry I don't know of any show breeders in the Kent area (only a few working ones who may have been able to help).
Apologies of this is obvious, but just in case it isn't... If I was planning to breed quality show type cockers, I'd be contacting the breed societies and getting in contact with breeders who actively show their dogs. I think the only way you would be able to convince them to sell you a quality puppy (with the possibility of future removal of breeding endorsements) would be to show your dog. And once it has been proven to be a good example of the breed and you have shown your commitment to bettering the breed, then they may agree to lift the endorsements and advise you on which lines/ stud to use. My show type cockers were sold to me on that basis. I didn't breed either of them, but the breeders were on hand to assist with grooming, showing and an agreement was in place that should I want to breed the bitch, I was to contact them in relation to lines that would be suitable and would complement my bitch. It wouldn't be a quick process, and would involve a lot of commitment, but if you are serious about breeding quality cockers, then that is the way I would suggest you go about it.