I am afraid it is FACT that you continue to wear the wings of the service in which you qualified.
NOW, whether you choose to go against it and wear those of your new service is between you and them! But by the letter of the QR's You should stick to those first issued. If you qualify as an Observer and become a Pilot you wear Pilots wings and the O's wings behind your lapel (NOT in QR's!!)
As for AAC wings on RN uniform it is reality!! As for RAF on RN uniform, I have seen that too with a Harrier Pilot!
Quad erat demonstrandem!
BUT overall, WHO CARES!!