Was also told by same person that the emergency row seats in the centre of the cabin were equipped for bassinets, therefore reserved for families! Might just drop a line to BA on that one!
You're assuming that the rules regarding children and emergency exit rows apply to the central row as well, in fact they don't. On a wide bodied jet the central seats in front of the bulkhead are generally reserved for people travelling with children. Think about it and it makes sense.
Some airlines will allow you to book emergency exit seat rows online and some won't, I think most won't.