i contacted a cocker spaniel breeder in my area to find out about her pups and their temperment, genes etc and she told me there had only been 2 pups born and their mum 'refused to grow a coat' for a couple of years, is this normal?

Which bit guest, the 2 pups, yes - the lack of coat replacement, yes it can happen the coat is closely connected to the sex hormones and an imbalance can cause the change in proper growth.