So how did oldnotbold get the opportunity to reserve his seat for free 48 hours in advance,
The point is that the promise to allow free seat selection 48 hours in advance was not fulfilled; when I tried to check-in 48 hours before the flight the system would not allow that. So I couldn't reserve the seats.
Maybe I missed something, but if I did it was not clearly shown. I've had a workstation/desktop on my desk every day of my life since it was a BA workstation in 1973 (my then employer piggy-backed on their system, back in the '70s), and although I'm getting old and decrepit I'm not yet a dribbling idiot, as far as I can judge.
Someone will now show that it is completely obvious how to reserve seats 48 hours in advance if you buy Economy Plus, and when that happens I'll dribble a bit and shut up.