I suggest you go to the new Cathay lounge in T3, as you enter the First area, the Pantry is on your right. Go to the end there, turn sharp right, and nab the corner sofa there, switching off the TV if necessary. It's at the furthest corner from the dining area and I suspect very few people will know of this spot. From 11:00 hrs to 17:00 hrs there won't be many people in First.