Free Traffic Legal Advice

The two large signs shown here, are the ones that count. The two small signs have no legal significance, but merely explain in English, the meaning of the large signs.
https://maps.app.goo.gl/86rtbY7jYmq13Mne7

These restrict parking to permits A-ML.  So where have you been parking if you have no permit and how have you avoided getting a PCN until now, as you say you have been waiting for years for a permit. So why within those years have you not been granted one ?

It's very important you tell us all about your parking problem, because getting a PCN cancelled needs a multi-faceted approach. If you've been waiting so long, have you contacted your local councillor about your problem; the officials will just bat away anything you say to them, but councillor enquiries are dealt with more seriously.

This is an off-street contravention in an estate car park.

It is at NTO stage - did you challenge the windscreen PCN?

From what you say you have an on-street permit but couldn't use it that day because of road works? There must have been nearby parking surely.

The signs are unauthorised if it's off-street. The CPZ signs in particular are redundant if what lies beyond is not a road, as indeed a car park cannot be a road.(but it can be a 'public place' for other road traffic purposes)

OP, where is the noticeboard which sets out the Ts and Cs of parking in this car park?

The 'controlled zone' sign and the 'permit holders only' signs are prescribed under the Traffic Signs etc. Regs which were made under the ROAD Traffic Regulation Act 1984(the clue is in the title). They are included in the Highway Code and its accompanying publication Know your Traffic Signs. As such, a driver is expected to know what these mean....but when they are used off-street they have NO meaning which you're required to know and act upon. If they have a meaning, including whether a failure to comply could result in a penalty charge, then this mist be stated clearly on one or more visible notices within the area concerned.

These are the signs within the estate and where I parked. The resident permit I was issued was for C-AN area, outside.

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Any ground for appeal ?

At the moment, I see none, because although you have a permit, it didn't apply to the location where you parked.
However, see what the others say, as HCA suggests the signs are not lawful because where you parked is not a public road, (at least that is my understanding).

You have been issued with a permit for a big parking zone so so you can't really complain you have nowhere to park on-street.

You can of course point out you've been on a waiting list for an estate parking place as I understand it.

But as said the council says the contravention occurred in an off-street car park. Such car parks are subject to rules about terms and conditions and as we've seen with other estates none seem to posted for people to read at the location.