Is Visa Required if transiting through PRC

Good Morning, thank you for taking my enquiry. I am an Australian Citizen traveling with an Australian Passport. I will traveling to the U.K. in May. Departing Sydney 1.05.15 and arriving at Guangzhou Airport on 1.05.15 staying overnight then departing for the U.K. on 2.05.15. On my return trip from U.K. to Australia I will be staying 2 nights 24 & 25.05.15 in China. Departing 26.05.15. please advise if a transit permit is required. Many thanks Mrs Peta Jackson.