In peppers case she was an unplanned pregnacy between working spaniels.
way back in yesteryear when working cockers were nearly extinct, working springers were crossed with show cockers, and show cockers were crossed with working cockers to add to the numbers and to get the working gene going again. that was a long time ago and it would be very wrong to do that nowadays.
If a sprocker is an exceptional working dog a gamekeeper may choose to breed of her / him, Im not saying its right or wrong but it is done now and again.