For me it'd be a tossup between CX and QR. QR is definitely my favorite but I don't know it's worth spending a lot more Avios on it, how many more Avios would you have to spend vs. CX? Plus you have to book 2 separate itineraries. Are you eligible to enter Qatar? In practice you don't actually have to, they will likely check you into both flights at NRT but by the rules (which Japanese follow to the letter) you have a ticket to Qatar, not the UK and need to be eligible to enter.

CX is good, and the HKG lounge is great (if you're eligible for the first lounges). I flew them TYO-HKG-AKL in December and had no issues with them, the A350 seats are quite nice as well.