Welcome to this long standing debate. I have also tried LHR-BKK in F a number of ways, -- BA to CX through HKG, CX through HKG, and QF direct. I find the QF seats not particularly conducive to sleeping, and far too many seats in the 744 F cabin. Also, there's absolutely no privacy in the F seats (note, not suites) on QF. Not even some type of enclosure as on BA, let alone a legitimate suite. That said, the service is warm and friendly, and the food is great.

BA has the standard BA 744 F seats, service and food. Service a bit formal, but otherwise a good and consistent product, both hard and soft. The seats do afford some measure of privacy, and the fact that they're angled out (window seats, that is) enhances that. And, despite the numerous posts on EF from others, I have never had a bad service experience in BA long haul F.

The new CX suites are unbeatable, IMO. Extremely comfortable, and well suited to a good night's sleep. I have always found the CX service perfect, but I am aware that some find it a bit on the subservient side. My CX FAs have all been appropriately solicitous, accommodating and, yes, friendly. If you like Asian food, then this is the hands down choice for you.

So for me, this route will continue to be LHR-HKG-BKK on CX, but try them all and see which you like best.

Enjoy !!!