Finally sorted the problem with the new 5D Mk2. Thought I'd test it out under the stars, with a one off clear night!
The wide shot is with the 40mm STM lens at f5.0. 10x2 minute subs at ISO 2000, and the other 2 with the 100mm Macro lens at f5.0 both 10x2 minute subs also at ISO2000.
Im pretty happy with them, and surprised at how much detail came out, especially at 100mm. Probably can't see on the low res version, but there is a fair bit going on near M20 and M8.
I'll post an Astrobin link later with the Hi-Res ones.
Thanks for looking
Erik