Welcome!
It looks like you've been well advised on most things already so I will just add some advice on trying to avoid the 787 if flying in economy, as the seats are much tighter than economy on other BA long haul aircraft, more Nightmareliner than Dreamliner.
Good news is that its supposedly very nice in WT+ and CW, so if you're paying for / upgrading to those cabins, then all we be well and rosey!