Credit the RAF with a little intelligence !
I can assure those who think that the RAF had never been told about QNH approaches that is not the case, in fact they a few years back changed to QNH approaches, however this did not best meet the operational requirements of recovering fast jets in bad weather usually using PAR.
So the RAF switched back to QFE, if you operate into an RAF airfield in an aircraft that can't use QFE they are quite able to adapt the system to enable you to fly the approach using QNH.