Stopping off in expensive Zone 7 (KUL, SIN) to get to cheaper Zone 8 (HKG) is going to be difficult to get past BMI, especially given that direct flight to HK are relatively prevalent.

Anyway, for return flights ....
Cash + miles Zone 1-7 60k+£405 J / 80k+£540 F
Cash + miles Zone 1-8 52.5k+£360 J / 70k+£480 F
Cash + miles Zone 2-7 as for Zone 1-7, so pointless
Cash + miles Zone 2-8 37.5k+£225 J / 50k+£340 F

Quite easy to spot which of the above is most attractive ...