Thanks Dave and Peter.
Dave, PI is a beast but I am def getting a hang of its basic tools. I do use StarX, BlurX and NoiseX but not always - a bit of trial and error to see what's working for the image at hand. For this image, the best stars came from plain RGB data (not LRGB, which I've been using) and I gave them a tweak with BlurX after arcsinhstretch-ing. I tried the new star reduction tools from BB but didn't like the result. I reckon you're correct about the coma and I too have seen it in recent my images but haven't had the time to see if I require slightly more backfocus ... bring on the Xmas hols
Alex