I just flew GCM/LHR/EDI and back again in the last week.... with one of my kids... and had no problem using OLCI in both directions... although I did note that on the EDI/LHR/GCM I had to pick up BPs for the second flight at the Fast Bag drop.

BTW, as an AA fan, I am rapidly converting to BA, as a) it is getting well nigh impossible to use mileage upgrades on AA out of MIA these days, and b) they now have WT+ on the GCM route, and I find those seats VERY comfortable for the overnight flight and definitely worth the price over coach.