You have to mentally adjust QNH to take account of the aerodrome elevation, I take it?
A bit confused I think - you make no adjustment to the QNH (altimeter setting) - that remains fixed unless told otherwise from a suitable source (ie ATC)
In theory you just add circuit height to aerodrome elevation to find the correct altitude to fly at.
In practise it's not even as difficult as that - you just get someone else to carry out this mathematical puzzle and fly at the published circuit altitude!
QFE is a quirk of the UK and is (as per usual) a result of old WW2 habits refusing to die.
IMHO there is absolutely no need for QFE.
I'm told that changing altimeter setting during the busy approach phase and having no idea what your clearance over the local terrain is can be useful to an inexperienced PPL. As an instrctor I find it causes far more problems than it solves. Forgetting to set QFE can cause havoc and be downright dangerous.
I'm sure I'll get shot down by far more experienced instructors but that's my tuppence.......