Bob, you can get some statistics through DASA's website. A quick look at their outflow table here shows the following numbers for voluntary outflow of trained RAF officers:
FY09/10: 420
FY10/11: 440
12 month periods ending:
31 Mar 12: 680
30 Jun 12: 680
30 Sep 12: 730
31 Dec 12: 890
31 Mar 13: 780
That's an upward trend in my book. From 420 PVRs in FY09/10 to 780 in FY12/13. Measure from 2009 to 2012 and it's almost an exact doubling in the PVR rate.
Interestingly, it shows the VW numbers as well (voluntary outflow of untrained officers, it says here)
FY09/10: 40
FY10/11: 50
12 month periods ending:
31 Mar 12: 60
30 Jun 12: 60
30 Sep 12: 230
31 Dec 12: 230
31 Mar 13: 210
So only 40 untrained officers PVR'd or VW'd in FY09/10, rising to 210 in FY12/13! That's Leon's hacked off guys in the training system, I reckon.
Of course, these aren't aircrew specific, but with so many blunties on short service commissions and happily seeing them out, I imagine the vast majority of these stats are from aircrew.