The AMS-LHR-CPT timings on BA are so much better than the QR layover, however!

Not the best product, by any stretch, but it's not too bad. If you're going to pay, pay for the upper deck - go big or go home! (Or at least take any cheap/free seat on the lower deck).

The good news is that if you do AMS-LHR-CPT you'll be very close to bronze and free seat selection seven days out. Do it twice in a tier point earning year and you'll be knocking on the door of silver and free seat selection at the time of booking.

(Also, both HKG and CPT are 5,995 miles from LHR - coincidentally or not, flights that are over 6k miles earn more tier points!)