Posting this as the final nail in the coffin of GIMP processing. I bought a Pixinsight licence this week and will start using it from here on out.
This was done last night, a bonus night that was supposed to be rubbish (the seeing was quite bad, to be sure), its about 38 mins of 120s subs each HA Oiii Sii with the WO zenithstar81.
I have massive sawtooth in my RA guiding and I was playing around with PHD2 settings during these subs last night. I'm also wondering how good the bahtinov is for focus... it seems with the micro control focuser knob I have a fair bit of movement there with the spikes not moving, but when I'm focused on a star with no mask and aim to make the star as small as possible there is a definite best point.
Anyway, this might be something like the end of the beginning, looking forward to what I might be able to produce in future!