I changed from O to C, it was available in kiosk and at counter on outbound and other one online. I didn't do this for points, just for comfort but I'm surprised that paid upgrade doesn't count.

I found it: C - Awards at 100% of flown miles and is used for Business Class upgrades only. I checked my account and avios was incorrectly posted showing y/o and y/q:
LOS ANGELES - LONDON HEATHROW (Y/Q) 20TP 1,364 avios, Tier Bonus 0 5,456 avios
LONDON HEATHROW - LOS ANGELES (Y/O) 20TP 1,364 avios, Tier Bonus 0 5,456 avios

So some correction is due as I should get 100% of miles flown before tier bonus is calculated, do I understand it correctly?

What a shame but it was still better than BA business class with 8 seats in a row. And cabin was deserted. Economy was so full that they put some standby passengers into business.