In the U.K, the vast majority of GA uses QFE. It does cause problems with people not changing to it when arriving at a field and other similar situations, but it is the norm here.
DFC, don't be facetious, we all know they are a multitude of differing cct heights in use, but most are at 1000'. The confusion comes, because there is not an easy way of working out your height, or how far you have to descend. Simple on QFE, but with QNH you need to think about it, whilst we are talking about VFR flight, why introduce an element of uncertainty?
I don't like changes being forced on people which aren't standard in this environment, unless there is a really good reason, otherwise it is a waste of time. PPL members used to QFE will ignore it. New students will use it, but you then have a situation where half are doing one thing and half doing something else leading ultimately to confusion somewhere along the line.
I can understand the reasons for it. I have operated on both QNH and QFE with an airline and whilst I understand all the arguments for and against, I prefered approaching on QFE, but very quickly got used to QNH, though it really required altimeter bug's on approach to try and minimise the brainwork.
However, if someone is taught from day one to use QNH only, then fine, it is only an issue if you try and force occasional flyers into a new way of thinking. You are asking for trouble there.
For IMC/IR, what does the school use?
It sounds like this has been an edict from on high and making changes like this without discussion or explanation is not good practice. If the FI's aren't sure why they are doing it, then what chance to they have when a PPL demands an explanation to the change. In this case it seems to be "'cos I was told to" rather than having coherent reasoning behind the change.