Originally Posted by ThatT1Feeling

Are you sure that the cabin is actually opened up or does it just look like that on ba.com?

My experience has been that the allocation of F seats is done only once the aircraft is under airport control which is with 24 hours of departure. I've tried calling the GGL line in advance and they haven't been able to allocate seats in F, whether they appear open or blocked on ba.com or Expertflyer.

One time, after MrsTT1F had only got home the night before off another very delayed longhaul BA flight, then the GGL line messaged LGW to ask if there was anything that could be done. Otherwise it does seem to be something you can't influence. I've never been able to select the F seats online, whether appearing to be available or not. Please keep us informed!