I have booked it directly with BA on the phone. Tried with the UK and German line.

Now the outbound fare is AFFJSA, inbound (via Tokyo) is CFFJSA.
The problem is that their system couldn't price the AFFJSA via Tokyo - although it's allowed by fare rules. They couldn't help any further. Also not with the second stopover.

I understand that there is no First Class on Qantas SYD-NRT but the AFFJSA should than book into J/C-Class.