The quill feed shaft is seized-on to the quill return spring housing so turns with it. I've tried heat, a puller and a hammer to free the housing from the shaft but all without effect. A drawing on the "Denfordata" site suggests that there is a circlip on some models but on mine there's nothing visible.
If I can't get the damn thing apart I'll take a saw to something and then either make a new spring housing or repair the feed shaft, but I'm hoping that someone here will reveal the secret that I have missed … ?