The saga continues, I saw today that there were now 2 seats just opened on the return for HND-DOH-LHR at 160K + £105 for 2 people. This was a no-brainer, both legs were in QR A350 Qsuites, and only 10K Avios more than the direct BA HND-LHR...and £770 cheaper in taxes / fees! I rang up BA again, and fortunately the HND-LHR change hadn't been ticketed yet, so yesterday's £70 change fee went away, and got a full refund as still within cancellation window. Pretty incredible to get ~18 hours of Qsuites for £105, it really drives home the excessive surcharges that BA tends to charge.

Given that it's only 5K Avios more than it would have been with a Barclaycard voucher (if the return was even possible) and £445 cheaper than my last night's "best case" price of £550, it's an even better conclusion! I suspect peak / off peak makes a significant difference in using the vouchers, as the outbound was off-peak, but return was peak. The outbound LHR-HND booking at 100K Avios + £550 for 2 is still a good deal in my view, and even worth the old 787 J. But even if the return could be married with the original, I'll take Qsuites, better food / wine and some exploration of DOH, the new garden, and lounges any day.

I think the learning here is to not automatically assume a voucher will result in a better deal, and always look at the price vs. product vs. schedule!