Here is a cheap deal flying to China which includes a free overnight stay each way if you connect in Xi'an.
Hainan Airlines will provide you with free transfers and accommodation for stops longer than 6 hours in Xi'an but not Changsha. You also get 2 free checked bags and food.
IWantThatFlight lists flights for $284 connecting in Xi'an which means 2 free hotel stays.
Google Flights is showing more of the cheap deals than Skyscanner/IWTF.
The cheap Melbourne flights seem to mostly be in May however are available from April to September. $284 is the cheapest but many of the rest are around $293 (booked directly from Hainan's website).
Sydney to Shanghai - Google Flights $316 IWantThatFlight has it for $298 including 2 free hotel stays.
You'll have to play with the dates to get a cheap price.
Melbourne- Beijing - Google Flights is also on sale for $284. 2 free hotel stays + flights for $284.
Most stopovers don't look long enough for a free hotel stay. This one has 1 free hotel stay on the way back. Another, another.
Sydney-Beijing IWantThatFlight inc 1 free night hotel. $298 or here
Went to Xi'an 10 years ago and was blown away by Terracotta Warriors. My miniature terracotta army.
I am sure everyone is wondering the same thing. Whether scotty has setup a new website for flight? :)