Sounds like you are just plucking jobs out of the air!
Pick a job and stick to it and convince them that you know as much as you can about it when you are interviewed.
If you are this indecisive about what you want to be - a commission sounds ideal for you!
As for an aircrew job, just wait a couple of years - at this rate everyone in the RAF will be given a flying suit and aircrew selection will be obsolete!
Good luck!