I was at Locking with a lad who got offered a job when he still had 10 months to serve but he was released early to take up the job.
As it happened he was still officially in the RAF which is why 8 months later he got picked up for promotion which considering the job he was in was paying £36K a year basic he strangely turned down.
I believe it depends on if your trade is over-manned, whether they can spare you or not and if it effects the RAF's operational ability at all.