Thanks everyone. The more I look at this one the more I like it despite the corners looking a little weird due to the sensor being too close. I did have the 'correct' back focus according to Celestron and ZWO. I've since added an extra 1mm of back focus and will see how that goes.
Dilshan - image was taken from my suburban backyard which is in a Bortle 5 zone. Interestingly, my attempts at stretching the image and colour/saturation correction were not as good as PI's auto-stretch process ('STF') - 1st time that's happened. So, I just transferred the STF parameters to the image histogram as a basic stretch and then edited the resultant non-linear image.
Alex - you have great skills mate! In fact, this was my first attempt at shorter exposures with higher gain. I did this based on your experiments from which I've learnt a lot. Instead of using 5min exposures at 120 gain, I used 2min exposures at 240 gain and couldn't be happier with the result; it seems to produce less noise (although I've not tested that hypothesis) than using longer exposures with lower gain.
John - I managed to fix (yaaay) the weird shaped guide stars by spending a bloody long time precisely focusing the guide camera in the OAG.
Dave - I too noticed the double lobe of the Homunculus in the stacked image and jeeeeeez I tried hard to get some detail out of it. But it was too overexposed. Made me wonder if a different optical train (for planetary?) might get in close enough to get some detail using very short exposures and 'lucky imaging' techniques?
Steve - I'm a sucker for little swirly bits in the gas/dust! I'm enjoying the SCT's longer focal length to get in closer to such things. I did try using my ASI482MC planetary cam to get even closure but the ASIAIR had trouble plate solving the very narrow FOV. At least I tried
The crescent stars (fixed mostly later) in the OAG were very off putting to me (worked fine) and it's funny, but when I went back to a guide scope the round stars felt like a breath of fresh air - weird 
