Bis,
I can't see any PVR stats on the DASA site either. However, the site does say that 'Voluntary Outflow is defined as all exits from trained UK Regular Forces which are voluntarily generated by the individual before the end of their agreed engagement or commission period.' I guess that's close to PVR.
The stats back to 2006 all show RN Voluntary Outflow is higher than RAF. I can't seem to access stats before that. Nonetheless, I think they could be considered relevant.