Neither show or working type Cockers are "traditional Cockers." Traditional Cockers were a shooting companion for the gentry, not a working machine bred for competitive field trialing. Neither were they originally heavily coated, heavier boned, or lacking in working drive as many show type Cockers are these days. In my opinion, BOTH types of breeders are very guilty for the separation in type in this breed.
Even though working type breeders are primarily concerned about breeding for biddability and working drive, they should also consider breeding to the standard. The breed standard is about maintaining structural stability and maintaining type. You want a Cocker that can and will move like a Cocker, and you want a Cocker that actually looks like a Cocker, which most working Cockers fail to do these days.
Worker or show, both are Cockers and both are amazing little dogs. There are plenty of gun dog breeds that have absolutely no split in show or working type and it would be wonderful to see that one day in this breed, though perhaps they are too far gone for that to ever be reality? It seems as if the best you can hope for is finding a working breeder that actually strives to breed to the standard and retain type or find a show breeder that strives to breed for a dog that is still capable and still eager to do what the breed was originally bred for. Unfortunately, both situations are difficult to come by these days, though it seems to be far easier to find a show breeder that also works their Cockers and titles them in the field in some parts of the world than others.
As for separating the two, there is no point since they are both Cocker Spaniels. Field Spaniels are a completely different breed with a completely different working function.
Personally, I think it's sad to see how working Cockers have exploded in the pet market. I completely agree that the quality in breeding of these dogs has gone down, because of the boom in interest in mere "pets."