Still, this are feeder flights to LHR, not BA having a hub in ARN. For passengers that travel far, LHR might be a reasonable airport to transfer in. But for most of European trips it is the worst choice in Europe. I would always prefer to transfer in CPH over LHR. Even on TATL connections I would say LHR is not that attractive. The Eastbound flight is too short to sleep enough, and then the trip is getting 1-2 hours longer than through the other hubs, you spending most time running around the gigantic terminal and its queues (the BA lounges are fine though, if you get to spend any time in them, that is).