I got chopped very early in AAC selection despite being better looking and from a better Corps than Yeoman!
I then spent the next three years split between watchkeeping and staff duties. It was perfectly possible to get the exams done around a 9-5 exsistance. Think I only worked 2 hours a night Mon- Fri and had weekends mostly off.
Book a GS course 6-7 months away to act as a focus, review the material finish the progress tests. (do not try to learn all the material off by heart!!) The brush up course is then the key.
You can use resettlement leave in your last 12 months in the green bit of the forces. I did a FI rating straight away instructed weekend to build hours. Completing an IR in my last three months of service worked well.
HP how's the electric jet?