Paul,
Not bad at all.. Tell me, Did you stack all the subs together? (ie, all the different exposure times?)
If so, thats not the best way to do it, as stacking will give you the average value of the pixels... hence the shorter exposures will kill out the detail in the longer exposures, and the longer ones will blow out the core a bit.... Its a good image none the less though..
Next time around, try stacking the sets of subs separately, then combining them together in photoshop using layer masks to gently blend them all together
a good guide on how to blend 2 exposures can be found
here
Alex