Richard sussed it! (Jools' mystery machine).
The machine is actually a TAPER GRINDER, used for grinding tapered shafts etc. I adapted it to shape guitar necks which require a slightly tapering D shaped section.The whole bed traverses left to right, but it also pivots about it's centre, which gives the taper. A cross-slide holds the grinder, or in my case, a router, and this traverses in and out to machine the work.
I found the machine abandoned when a factory closed down so it cost me nothing, (though it's a massive weight, it was no fun getting it to my workshop).
Jools