Been playing ...I bought a copy of Noel Carboni's Astronomy Tools today for Photoshop.
I'm still getting my head around them, but they're easy to use, and I can highly recommend them.
The actions used above are; Light pollution removal, Make stars smaller, Increase star color, Soft color gradient removal and a small amount of Star diffraction spikes (not really visible in this image).
Warning: Be prepared for loads of pretty pictures with star spikes all over them ;-)
Like these... hehe.