Your post doesn't make an awful lot of sense about the metal shaft coming away.
These knobs typically have a split boss on the back that is a push-fit onto a shaft sticking out of the cooker, said shaft having a flat machined on it. The knob usually has a spring collar round the boss, that ensures a tight fit on the shaft.
If I understand your post your knob has broken at or around th eboss and the spring clip has disappeared.
If my understanding is right, I can tell you that replacement knobs (complete with spring collar) are available.
Try these outfits, or even EBay
http://www.espares.co.uk/search/ma2322pt1599/cookers-and-hobs/knobs/rangemaster?&mkwid=sQVGKLSab&pcrid=74378026621&kword=rangemaster%20cooker%20knob&match=b&plid=&pdv=c&gclid=CPX80q3PlcsCFVG6GwodwOYOrg
http://www.rangemaster-spares.co.uk/cooker-oven-spares/catalogue.pl?path=156166
XXX, February 2016