I have never felt any pressure to pass (or fail) anyone and, if pressure were applied, I would express my views in a "full and forthright manner"
and then ignore it.
As for some examiners being easier than others, I think it's a myth. Examiners have differing personalities (some seem not to have a personality
) and this makes them seem easier/harder. At the PPL level I believe the basic judgement that we all apply is: "is this person safe, do they know what they're doing and would I let my family fly with them". They will pass if the answer is Yes and fail/partial if the answer is No.
Some schools may have a low failure rate but I suspect you'll find a correspondingly high number of "progress checks" being performed by senior instructors (who happen to be examiners); this shouldn't be a concern. There is a concern however about schools that have an examiner on the staff and offer a fixed-price PPL - but fortunately there aren't any of these in the UK (
AFAIK).
With the exception of this final situation I don't think there's a problem to fix. A simple letter would seem to be in order if you have evidence of an individual examiner who's been nobbled, rather than creating a new bureaucracy that would need to be paid for.
HFD
(edited to sort-out some grammar)