I seem to remember that when the military abandoned their 'QNH only' procedures, they also abolished local QNH; departures were supposed to change from QFE to SPS on climbout and vice versa on descent; if staying below transition altitude, only RPS was to be used. Of course this meant that Northolt, Benson and Odiham, being in or below the LTMA, had to operate non-standard, which met a lot of resistance especially with new controllers straight from Shawbury!!
Never did get a reasonable explanation why the military chose to revert to using QFE, especially as the change was very poorly notified, whereas the change to QNH procedures was well planned and executed, with the excellent Dave Harrison visiting most units to brief them. I WAS told it was because an 'elderly gentleman' (senior officer to those unfamiliar) cocked it up one day on a check ride thinking he was on QFE and trying to descend to zero on his altimeter, but that was only a rumour.