(Ex BA staff here)
Assuming T5? Try your booking ref in one of the self service machines just in front of check in..if you have a seat , all well n good,print your boarding card, dump your bags at the bag drop desks and off you go. If no seat allocated, have a chat with one of the many staff hanging around the self service machines. I've always found them really helpful. Which flight are you aiming for ? I can check the loads if you like x