Thanks for the try Paul, but unfortunately not.
That just brings me 5 different [net_hostnames] values.
After some reading of Documentation/Forums, I have come to believe that M_HOST_NAMES is part of a much more complex system, of internal network mapping. Not something that I as a mere application/report developer really understands (or if I am honest, wants to !)
I think some people might have a less complex infrastructure than I seem to ... and so the above does work for them though.