I was there a few days ago, and carted all my luggage over to the Jewel check in to find no sign of BA. Just short of 4 hours before the flight. Lugged my luggage over to the premium checkin, and asked there and was told that after 5pm BA dont bother with having check in at Jewel since their own check in desks are open. No mention anywhere online of that of course, so great fun to be had pushing your luggage all over the place.