Chris - are you still looking for an answer for this? You might want to give these guys a try...
http://www.glasweld.info/scratch_index.html
I used them to repair scratches on my car passenger window, and they did a great job. Not sure about double glazing but, like you, have just discovered a couple of chips in our window so am considering giving them a call.
Alex
September 2009
Only by replacing the entire glass unit, Chris.
John
July 2009
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix windows and doors.