I mean what are the course entry requirements as they seem to be different at every flying club + school I have checked with
They really shouldn't be! That would just make me think those schools don't know what they're talking about.
I believe it's 150 TT for fixed wing to start the CPL flying course (155 for rotary).
The flying syllabus isn't much different to PPL in essence but it's just to a much higher standard with more judgement required. For example, with helicopters, a PPL examiner would call the engine-off landing to land at a particular spot whereas at CPL you call it yourself and judge yourself whether you are committed and close the throttle.
Cheers
Whirls