OP, at this stage I suggest you just stick to the basics of why and for how long you were there, who is the registered keeper and are their DVLA details current.
By the way, it's very sensible of the council to switch off the meters on days when parking is free, which begs the question: why did you even look?
Is this simply a case of you parking on a SYL and being unsure of the restricted hours consulted a P&D machine and on finding that parking in a parking place was free assumed the same applied to the SYL? Quite common I would think.
On another point, if the CPZ sign posted by Incandescent is still there then the contravention grounds are incorrect because loading is also prohibited.