Having just flown (premium) economy on CX, I didn't think there was anything much to recommend it versus BA - some things better, some things worse, but not worth paying 25%+ extra for.

If you're going late November then you should get the A380 on BA25 which would be fun for novelty value if nothing else - not sure exactly what date it comes into service (someone will be along to tell you shortly, with appropriate caveats) but I picked a couple of dates and can say it's definitely after the 10th but before the 24th. If you get Y on the upper deck then the window seats are pairs rather than triples, which sounds like something you're looking for. If you're on a B744 (currently scheduled for that route pre-A380) then there are 3 rows at the back of Y where the fuselage narrows which have pairs by the window, though you might have other reasons for wanting to sit further forward.