As a breed, I don't think Cocker Spaniels tolerate long periods of solitude very easily - certainly separation anxiety crops up quite often in relation to owners wishing to rehome a Cocker & it's one of the reasons why many breeders will not sell puppies to homes where the owners are absent for most of the day. I agree with Pam that getting another dog is not necessarily the answer - certainly not a puppy anyway as puppies have a habit of following an older dog's example (& puppies should not be left alone for long periods anyway) I do know of a couple who had this problem with their Cocker & did take on another older Cocker - this did improve the situation though did not totally cure it. I believe Peter Neville, the behaviourist, has produced a pamphlet on separation anxiety which you might find useful (you can order it
here)I would tend to agree with Pam though that you need to find some way of breaking the day up for your Cocker (if you do work long hours) such as employing a dog walker or perhaps you could consider day care at a local boarding kennels.