Craig, what exposures have you used and how many frames? Jon has minimized the red and blue splotches which are very evident in the bottom right hand corner of the images (where the skyglow gradient is the worst). Cooling the camera will fix this
Well, without cooling - longer exposures and/or a bigger piece of glass to capture as many photons as you can to improve on the signal to noise ratio is the trick. Dithering can help too (bumping the camera off target by a tiny amount between frames. Noise internal to the camera is then moved about over the final image, but because it only occurs in one frame in that position and not all the frames, the stacking software rejects the noise. It's like magic.)
All is not lost though. A quick process with Noel Carbonis Astronomy tools cleans up you image a bit, and this is real cheap software. I have binned the image with Nebulosity to remove the grain (possibly from jpg compression?)(with the original files I would not do this except for web posting as you lose resolution for printing), then ran Colour Blotch Reduction, then ran light pollution removal enhanced flatten, then Auto Tone, Auto Contrast, Auto Colour. Then jiggled the colours with Colour Balance to line up the histogram R, G and B. Then Deep Space noise Reduction. Then Auto Tone, Contrast, Colour again.
Mark.