Hi Ian,
It was suggested that I respond to you because I can print via my Canon MP600. All I did is plug in the printer. The only thing I can think of that you may not have done is that perhaps your Canon is mislabeled. This is what I would try: Go to Canon's website and under support you can get instructions on how to re-install all the drivers after you delete them. Do that. Then, when you plug in the printer anew, name it with the place you are trying to use it in parenthesis, e.g. Canon MP600 (Airport) or Canon MP600 (USB) or Canon MP600 (Bluetooth). It seems that the printer needs to be added as many times as places you want to use it. I have it listed twice (Airport & Bluetooth). Then I made sure that the bluetooth setup is set to recognize the (Bluetooth) printer. I have no problems printing via airport or via bluetooth.
Lastly, I spoke with Canon, and they agree that this printer is unable to ever do anything other than print via airport & bluetooth. If you want a wireless printer, they suggest the Canon MP800R. I'm going to look into that option.
I hope this was helpful.
Cheers,
Spencer