Might be able to shed some light on this - I passed my CPL there early 2020...
The keys have always been in the aircraft folder, was like this since day dot. Had never heard any issues prior to this one of other students grabbing an aircraft without permission (although I once grabbed YWM instead of YWN and we didn’t pick up on it until after the flight).
Scuttlebutt at the time is scheduling made a human error and swapped him out from a Vixen to a Bristell while working on the schedules.
In terms of progression, I was given a flight schedule at the start of my CPL which did have 3 famil flights to be completed. Majority of my debriefs (I have some copies still) usually end with “next flight xxx”. However was pretty aware of the next flight anyway.
The general process for getting ready and being signed out was - Grab folder (had keys, MR, dipstick) go and preflight plane. Either before or after this do all your flight planning, then fill out necessary paperwork (you had to fill out a risk matrix for each solo, regardless of where you were in the syllabus). Once that’s all done you have to grab an instructor and depending on the matrix you grabbed a grade 1/2/3 and they checked. Licence, Medical, MR, planning, ASIC, Matrix, W&B, your hours on type (cant remember if anything else). Then once they were happy they signed the matrix and then despatched you on the system. Post flight you also needed to see an instructor to discuss any issues.
From my perspective I never had an issue speaking up to someone and at that stage the chief instructor was very approachable.
Apologise for any poor formatting/grammar. On my phone typing this!