Not bad Chris!
What image acquisition and calibration software are you using?
Generally, artifacts in your images can be removed by:
a) dark frame subtraction. It's best to take at least 3 dark frames, median combine, then subract that median dark from your lights. Auto darks (at least in CCDSoft) mean only 1 dark is taken and used for all images in a series.
b) hot/cold pixel removal (eg as in CCDStack) after calibrating, registering and normalising your images
c) you could also dither your images by a few pixels in between light frames so when they're median combined artifacts dissappear or are minimised. 3 subs is the minimum for a median combine but 6 or more is best.
d) Doing all three of the above is even better (that's what I do)
Cheers, Marcus