Thanks for the comments folks.
Shy Torque: Your absolutely right (except I can't confirm the apocryphal "Airship in a Chippie tale............"). I've advised the powers that be that in this day and age it makes sense to standardise on QNH, especially given that new transport types will have civil cockpits in most other respects.
I've informally asked a few of the mil pilots in my team, all of whom have said that they can't see a problem in switching to QNH. Given that the cost of providing special-to-type cockpit software for a few military versions of what is otherwise a standard civil fit is potentially pretty high (and presents safety critical software integity issues as well), it seems that it's a no-brainer to just change procedures.
VP