I beg to differ slightly with your opinions there. For one, the RAF frock was 'borrowed' from a RN design and there were notable places were RAF kit was developed over standing RN gear. Conversely, I've read of chaps in the navy who found their gear inferior to that of the RAF and so used patterns, like the 1941 pattern vest, to wear instead.
As for that film Alex, the Battle of Britain and mostly any other ww2 film shows that the kit has never really been depicted perfectly in a film. Even films filmed in wartime Britain have got the kit wrong! I think that you can never really have a good idea of when and what kit was used for if it was never fully recorded by the AM. Nigel's vest shows this.