Welcome to Flyertalk jk156. I'm not able to offer much advice about the internal seat selection issue, other than the obvious one of trying via QF's or Qatar's websites. But welcome to the British Airways board and I hope you have a good flight to Australia. Welcome on board.

For the CW availability, it's actually not a bad route for availability at the last moment, typically 3 days or so from departure until the day of departure. So check once a day to see what happens. The seats get released around 01 hrs London time so if it's important enough, plan on staying up late and have the Tokyo BAEC telephone number handy, number in the Dashboard. You can't read too much into Expertflyer about Avios availability. I've been doing it for years, and I'm able to guess some of the time, other times it can seemingly go fully random, including availability coming up on a flight I knew to be heavily overbooked!