I didn't make the grade on the Pilot Aptitude test at OASC when I was sixteen but was given a Flying Scholarship and told to come back at eighteen. I re-applied at eighteen and failed the aptitude test again.
Back in 1975 I completed the Selection Officers Course at Biggin Hill and that involved looking at the aptitude selection process. We were told that you only ever get one go at the aptitude tests, if you really failed first time, you won't get a second chance. If for any reason you go back for reselection, because you failed selection for some other reason, the aptitude tests on the second run are conducted but the scores from the initial set are used. The reason given is that you can learn how to do them. Some of the staff could get very high scores. They also used to exchange scores with Hamble if candidates had conducted their tests.
Back in 1968 a bunch of pilots graduated from Hamble with SCPLs, there were no jobs for them, and 3 to my knowledge joined the RAF hoping to become military pilots; they were all trained as Navigators.
Things have changed a lot over the years and I see lots of military pilots trying to obtain civilian licences, I don't see or hear of many reversing the direction.