I always write about this on the surveys CX hands out sometimes. There often isn't a space on the survey but I write it somewhere anyhow.

Keeping conversations like this going hopefully help too. Maybe someone at CX will notice and start shortening the announcements or getting some out of the way before takeoff.

The most vexing PA is the "Excuse me everyone, if those bumps didn't wake you up please let me wake you up. Just in case you didn't notice we're passing through an area of rough air. Please make sure your seatbelt is fastened. We're going to stop serving coffee and other hot beverages for a while. Don't go back to sleep because in about 2 minutes we're going to repeat this announcement in Cantonese. If you still manage to go back to sleep we'll wake you two minutes later for the Mandarin version. I apologize for my extreme verboseness and any other inconvenience caused. Repeat in Cantonese. Repeat in Mandarin."

I think it would be much classier if CX made no announcement at all but just went through the cabin to check for fastened seatbelts. Any non-complying pax can be woken and asked personally. I think they check anyhow so why use the PA?

Don't get me wrong GB, CX is a fantastic airline. This is just an area for improvement.