hi Paul - very nice image.
Try deconvolution in IRIS with an actual PSF as the kernel to tidy up the stars - will also restore some detail in the galaxies, but care needed with saturated star cores. the examples given in the link are hideous, but good enough to get across the idea.
http://www.astrosurf.com/buil/iris/t...2/doc30_us.htm
Failing that, Startools does a nice job on cosmetics, but generally needs some manual mask editing to ensure that only isolated stars are adjusted.
regards ray.