I ended up booking OSL-LHR-SIN-BNE-HKG-BKK-LHR-OSL

Positioning from LHR the evening before with a night in Oslo.

SIN-BNE on Qantas A330 new J in 1-2-1 config and then returning BNE-HKG-BKK on Cathay A330 1-2-1 config. At the moment ExpertFlyer says the HKG-BKK is long haul config but I understand these are often replaced for regional J last minute.

As a solo traveller would you recommend stumping for the seat reservation fee on the BA legs (ironically free seat reservation on the QF and CX legs) or take my chances looking for a single seat at T-24?