Challenging a PCN OPINIONS please

[swifty]

I received a PCN yesterday for parking in a contractor parking bay, I've decided to challenge it because the car park is in a bit of disrepair.

I could see there was quite a few parking bays with 'C' in them so I parked in a bay that had no 'C' in it, When I came back to the car there was a PCN stuck on my windscreen.

The PCN says I broke Contravention Code 85 Parked in a permit bay without clearly displaying a valid permit, surely the notice in the car park has to clearly say 'permit holder only'.

Please see attached pics and tell my if I stand a chance of having the charge written off.