In theory it's a simple "contravention did not occur" and "penalty exceeds applicable amount".
But the reality is it's not as simple as that as it will come down to proof.
Was
pcn
issued less than 14 days ago? If so, what I would do at this stage is to write to the council and say I was not parked in x street on the day in question and in any event x street has no parking restrictions.
If more than 14 days ago wait for the NTO.
If council reject informal letter (if less than 14 days) or in any other circumstances, scan and post both sides of the PCN and NTO after having removed
personal data
and references.