By stating 'no returns accepted' on new items it is admitting in black and white that you are going against the consumer rights under Australian law.  A buyer could take it as such.  What are you going to say 'oh, I didn't mean it' if they leave you a negative over it?  It holds no weight. 
Better to accept returns - you don't have to do it on ebay's terms, but you do have to make sure you're not breaking the law.