The BA lounge is nice, the food is average, the champagne bar not too bad and it's quite comfy and has some good views. CX probably has better food options but not so great in other areas.
If you're WP you can enter BA F side of course. Noting that you mention using your WP card but if it's not the same card you're crediting your flight to (unless it's an award flight) you may face issues at some lounges....