Sorry, I meant to come back to this thread earlier. I created a download for all of my active listings, but in order for that to have worked the way you need it to, it would have to provide fields for individual variation quantity so that you could find all with 0, or sort each item (rather than each listing) by quantity, but eBay (at best) only provides a global quantity for summary purposes.. (That's near as I can tell, anyway, I don't know if it's me or the system, but when I load my reports into the spreadsheet, I can't make head nor tail of the information, it's all over the place with lots of fields with errors). 

Sounds like the best option would be the inventory tool, but I had a look at that too and I couldn't see a way to use it with current listings, only to create new ones. Hopefull someone who uses it can provide more info on that.