Thanks Greg, Andrew, Hugh and Mike. I have managed to reduce the pinky candy colour of the main nebula. Playing with PS settings I discovered that adjusting Hue/Saturatio of Red and Magentas did the jobs. Also saved at 8 bit mode allowed larger file size and quality. I chose 80% quality and 45% original size.
Link to 10Mb file:
http://www.astrobin.com/full/51505/?mod=none
Regards
David