I am a GCH travelling with a BCH on a UK domestic in August on a HBO fare. If I look at the seat map today, all of row 1 and the AB and JK seats of row 2 are unavailable to reserve. However if I do a dummy booking for just myself (GCH), for the same flight, I can select all of those blocked seats. Why can I not reserve them on my existing booking. Is it because of the BCH in the booking?

Thanks
JF