RAF and RCAF aircraft, the roundel does move to accommodate the codes.
Squadron Code generally goes ahead (to the front of the plane) of the Roundel Insignia.
Aircraft code to the rear.
This is about as consistent as the direction the wind blows.
We need an expert...not a modeller...to tell us whats going on.
And I promise I won't argue about the use of FS Standard Colour Codes*
(*an American wartime Aircraft Paint system)
for correct British RAF colours...sheesh...modellers!