After some more analysis at the individual subs for M13 taken on the 12th May 2012 it is apparent that their is trailing in the stars due to poor guiding. This combined with poor focus (which could be a result of tracking errors) and poor seeing I think has resulted in a lower quality image, lacking colour and sharp detail. The image itself is still good in my opinion, but I was expecting better.
Take a look at the image here, this is a crop from the top left of a sub, stretched so you can see it. I know this isn’t my usual spacing issue as the stars are not elongated toward the middle of the image (they would be stretched toward the bottom right in this image) but instead they are rotational.
I knew I had a balancing issue due to adding more kit to the mount and not correctly balancing it, this was shown also in the PHD graph which was far from flat at times. Unfortunately, due to rushing and trying to make use of the only clear sky in months I wasted it with these mistakes. I know for next time. Until then, clear skies!