I'm shortly flying LHR-JFK on AA in J on a BA issued ticket and codeshare but AA metal. I'm a BAEC member.

The AA flight departs from T3 at LHR which I've never used before. My understanding is that the AA business lounge (Admiral?) isn't up to much. Will I be able to access other OneWorld lounges at T3 and if so does anybody have any recommendations?

Thanks.