Oh yes indeed, I totally agree. My friend booked it without telling me because we'd send round a group message to let everyone know which flights we'd booked.

He's not so experienced with BA so wouldn't have foreseen this issue and it was too late once I'd found out (plus he was pleased with himself for getting on the same flight as us)

I suspect my situation won't be uncommon though - a less knowledgeable friend booking an HBO fare and wanting to sit with you - hence I thought it'd be worth discussing.