Thanks Marc and Allan,
I wasn't aware of HLVG but will certainly give it a go. I had tried desaturating green but that didn't work at all. I also totally agree about the star colours. Not very good. As I said, collecting colour data was very difficult. The images just do not pop out over the noise. I'm sure I needed longer sub frames but I was having so much trouble guiding I was ruining too many images so limited myself to 5 min. I've got to solve this issue before I try anything else. At the moment I'm not figuring it out...
Thanks,
Peter
Edit I think HLVG did the trick:
http://www.pbase.com/prejto/image/151603452