Ah the old "what is the use of QFE?" debate. What larks, Pip.
Of course its of no use whatsoever (except one see below) and we should all use QNH. But I confess I do like it when the altimeter reads circuit height in the circuit and zero on the ground, its kinda comforting.
By the way I thought RPS didn't exist beneath CAS like the London TMA?
One fun use for QFE - confusing your students to see if they understand how things like altimeter setting, terrain clearance, base of controlled airspace, and the effects of changes in pressure as you fly towards a depression, all work. Seriously, this is important stuff and if they can't grasp QFE and QNH then they need some more help in this area.
H