Why does one need to announce that you're flying in paid C to HKG? If you have a business class ticket - whether it's free or paid, you are entitled to the lounge.
At SIN, CX uses their new lounge called Skyview Lounge. For information, go to:
http://www.cathaytalk.com/showthread...=5614#post5614
Scroll down to Letter "S", post # 17.
There is a BA/QF lounge as well. You may use that if you wish by showing your BP. But there will not be any CX flight announcements there.