Thanks Marc, Greg, Mike, Al, and Paul,
Some wonderful ideas and tips gratefully received from your good selves.
My final revision here in high res.
http://www.astrobin.com/153116/D/
I have applied selective NR, selective sharpening, fixed the dark haloes around the original RGB stars, minimized artifacts, and used Selective Luminance layering from my original and re-composited versions. After umpteen iterations and variations I have finally arrived at this result.
I hope you like it, I've sure learned heaps from everyone doing this one, and all the constructive input is very much appreciated!
Clear skies
Andy