I've decided to add one final process to the image.
It is a stretching function I developed in Pixinsight where the pixels are mapped to the following function newpixelvalue = oldpixelvalue*exp(-0.2*oldpixelvalue).
This function allows the fainter areas to be stretched without increasing noise in the background.
High resolution here:
http://members.iinet.net.au/~sjastro/Lagoon_test3.jpg
Clear skies
Steven