There seems no direct flight from Hong Kong to Xiangyang. I suggest you fly via Shanghai or Beijing.

Maybe u can take a flight to Wuhan and then take a train there

Xiangyang city is not a major business city in China, only have 4 flight line to Beijing, Shanghai, Guangzhou(canton) & Shenzhen.

If you want to fly via HongKong, you need take shuttle bus from HongKong airport to Shenzhen airport (it's two nearby city just 45mins way)

Ms.Daisy & Mr. Feng are correct, there is no direct flight from H.K. to Xiangfan. And Wuhan is an other option with flight direct to HongKong. From Wuhan to Xiangfan, the distance is about 320km, it's 3.5hrs by bus, or 2 hrs by high-speed train (personally prefer), or 4hrs by normal train.