The use of 12 as opposed to 16 isn't a guaranteed winner IMO, I've tried this previously and the adjudicator was not persuaded(but I won on other grounds).
The single (PPA) sign as opposed to two isn't a silver bullet either, neither is the total lack of 'zone end' signs. The PCN seems compliant. I don't see that the council's photos can show much other than that the car was parked. There are 3 different entrances into this zone and you could have entered via any of them.
IMO, you should return and note the location of all PPA signs and Zone Ends signs in the area bordered by Wilmslow, Grandale, Claremont and Viscount.
To take an example from GSV, although this might not be current. You referred to a PPA sign at the other end of Hibbert. This faces into Hibbert from Claremont. So, if you are in Hibbert you are in the PPA. And if you go past this sign.....you are still in the PPA because it's not facing you, there's no Zone Ends sign and therefore Claremont is in the PPA.
But it isn't. Or, if it is, then why have the council chosen to place a PPA in a side road off a road which is already in the PPA at this location but not where Hibbert comes off Grandale?
You might need to read this a few times to get the gist!
But now I'd like to see a plan with all PPA and Zone Ends signs in the quadrant which I've set out.