I have done a lot of research on this kind of thing for a book I have been writing for a while (decades).

About a quarter of all British pilots were non-commissioned ranks, though there was little restriction regarding promotion. The criterion for advancement was based upon success / survival, e.g. George Gilroy (a sheep farmer) attained the rank of group captain before he was done. Also, many Commonwealth countries (Australia, Canada, South Africa, etc.) had their own training programs that were not rooted in rank-by-education and many of these airmen were funnelled into the RAF.

After the war, it was not unusual for the best of these men to be retained in the armed services, but with a reduced rank. Perhaps this is a reflection of the class system only being relevant once the crisis had been averted?