I do know of people who have been allowed to leave on PVR before completing their full return of service but it did need managment support to say quite clearly it was in the interest of service and person they go early. But you would still need to speak to your managment to convicnce them, so as has been said above why not just go and chat through your concerns and worries, you will be amazed how many of your bosses will actually understand and try to help you (any decent boss should see that as his most important job and trying to help the guys is far more interesting than just normal stuff!!).
I bet you waited a long time to get in the RAF and had to jump through a lot of hoops, so to throw it away in your first couple of years is a waste not just for the RAF but more importantly for you. Dont sit there not happy contemplating binning it, go and talk it through with your sncos, your sgts, FS or WO may seem unapproachable grumpy old gits but most will have been LAC/SAC and needed a bit of advice in the past so will know how it feels and be happy to help you and can probably offer some good advice and make things happen if needed.
In the current climate I would not be suprised that if you pvr'd you found yourself out quicker than you expect with no chance to pull the pvr, so before you do something that you may regret for the rest of your life thinking "what if....." , talk to someone that can help and at least try somewhere different before you jump.
So ends the gospel according to Harry!