Thanks so much fmac!!!
http://www.abc.net.au/tv/thecheckout/episodes/ep03.htm
Or there is information here about your rights. http://www.accc.gov.au/consumers/consumer-rights-guarantees
You may find you might want to drop in that you will speak to consumer protection. I would think based on what is happened you might actually be able to get your money back rather then then just replacing them.