OT: CX lounge at LHR T3 is vastly nicer than AA's....
It provides very nice noodles, drink, and quiet, calm seating areas ---- and opens at 8:30 am.
Whether or not the OW policy has changed (I recall using the CX LHR lounge several times when travelling on AA J or F without OW elite status in prior years), you'll be well-off at the CX lounge beginning shortly after your arrival.