I've had another go at processing this one, this time using IRIS with Bias frames, then similar stretching, balancing and a smidge of sharpening in photoshop. Only used 6 of the 5mins lights - one was a bit oblong on 2nd look, probably due to gusts on the night.
Feels a bit more natural. Even though a lot brighter the diffraction spikes don't seem to be anywhere near as washed out.
Used a hodge-podge of the IRIS tuts at:
http://www.saratogaskies.com/article...tml#IRIS_Setup
http://astro.ai-software.com/article...dslr_iris.html