Done a fair amount of research into this, because I'm attempting the same on my Omega.
For stonechip resistance, there was always good old reliable Hammerite, however, the classic car restorers are all looking at either stuff called POR15 or Mastic 121 now... Hammerite doesn't have the stone chip resistance it used to, apparently.
http://www.volkszone.com/VZi/showthread.php?t=461431It's £40 a tin, but you get a litre, and thinners. Compared with Hammerite at my local shop, at about £12 for a little tin, it's actually cheaper. It's a two-part paint (mixed at ratio of 50/50) which dries rock hard and is meant to be incredibly stone-chip-resistant.
Only thing is it's difficult, like hammerite, to get a smooth finish, without leaving obvious brushmarks. Takes practice, and I'm getting there. However, for your purposes finish probably isn't crucial.
Alternatively I've got me a trade can of Stone Chip aerosol, and a tin of satin black spray paint, both £4.99 each. Thinking of using this on my wishbones and dampers. But chassis, rough cast parts etc will be getting the Mastic 121 treatment, followed by a liberal coat of underseal spray.
