Purely anecdotal but....

I always pre-select a seat as early as possible and check in online. I usually travel in WT+ or CW via UUA or ex-EU. Blue to Silver in '14 and Silver to Gold in '15. BA op-ups are running close to 50% from WT+ to CW. No op up from CW though only 2 sectors had F.

My best was this year, AUS-LHR WT+ to CW for a red-eye. I nearly kissed the guy and cried. (Was severely hungover I hasten to add...) 😂

Edit: I also just realised that this was my only BA long haul this year not in CW or QR/CX J. 50% op up record maintained and BA might just have proven their op up strategy...