Welcome to Flyertalk MotherInferior and here at the BA Board

Same as mikeyfly, 6/7 K are good and I'd pick them but be aware 7 only has one window instead of 2 but........as it's an overnighter that isn't really important.

https://www.aerolopa.com/ba-77l

Here is the 777 thread and it's a 77L your on as in the Wik at the top of the thread linked below and I suspect your post will be merged into there.

Seating guide: BA Boeing 777-200 B772 | 777-300 B77W

Enjoy your flight and any feedback on here afterwards is always appreciated!

Pete