There are several groups that specialise in the minutea of WW2 and post-war RAF uniforms and they may be in a better position to say what is "correct" for any particular period, given the original wearers of such are getting fewer as time passes. Try
ww2rafgroup.org and
ww2rafgroup.org.downloadsguidance1.html
in particular for an overview. Having met a few members at various events I found them to be approachable and interested in such questions.
Ripline