I met a woman today who had a 2 year old show Cocker (though he looked more like a working) and she was struggling with some of his training, but when I whistled for Posie to come & sit, he paid attention to me and even allowed me to approach without him barking, which she said was very unusual. I suppose you've either got it or you haven't, eh?
I recommended she get's a whistle and get's started with this instruction.
Thanks again TopBarks. This has been a very helpful page.