Avios are so stressful to use in China and aren't a great value except in certain situations.

Basically the only time I ever use them is when I need a last minute PEK-HKG or PVG-HKG. Revenue tickets to Shenzhen and GZ are Always affordable, so really the only use is when one NEEDS to be in HK.

Also, there's the 50$ or so fuel surcharge that makes them even less valuable when a revenue ticket is $100

Using CTrip should be about $100 for Changsha-Chengdu, and another $100 for Chengdu-Guangzhou. The through-train to HK is about 30$ if I remember correctly