What do you mean by ".....taking the Queen's shilling for God know how many years..."?
There is a significant difference between the volunteers who man the RAuxAF squadrons and personnel called-out under the provisions of the Reserve Forces Act. One is a clear volunteer, the other is being required to respond to a reserve liability which he/she probably never expected to be realised..
I'd be willing to bet that there are quite a few folk around who left under PVR but who have probably have absolutely no idea of their liability for call-out (and/or recall - there is a significant difference) when the appropriate Order is enacted by SoS Def.