Well ! what a response, I did see something about Eclipse Auto Punches somewhere (sorry but my M&W 280 was my main concern so did not bookmark the page) the missing part is most likely the little detent spring Richard S2 mentioned, one bloke found a spring that fitted and got his working ok, in my case I hope the ball is a standard size, I have had a look at Moore & Wright's website but could find no reference to the 280 at all and of course obtaining a couple of replacement balls from them and sending them to Australia to boot, a comedian could develop a very good joke out of that!
Martin King 2, are the M&W centre punches in your collection (dare I say it) all minus their balls, if not could you as was suggested pull one apart in a plastic bag so you could measure a ball? I have checked out any old ball races I have in my workshop but all too big, not sure yet what local suppliers carry, I can buy a replacement auto punch made in China but it is against my engineering principles to have a first class tool out of action because of my momentary stupidity, might be time to make a ball turning attachment and tackle some silver steel then harden the right sized ball when found, then I can post the size here!
Thanks all who took the time to reply.
Wade VK4WM