Really? So what actually happens at T-72? The BA computer allocates you what it thinks are the best combo of seats left, but doesn't let you do anything with them until T-24? Sounds slightly barking to me.

If you book as a family, BA should allocate seats immediately. I'm not saying that the pax should be able to change those seats (thus not keeping good seats away from status pax who book later) or even be told what seats they have been given, but I can't believe that anyone would have a problem with seats being quietly allocated.