I'm sorry to say that the signage is perfectly valid because once you enter a zone, you must assume the zone carries on forever unless and until you pass an "
end of zone" sign. If there were no repeater signs in a very large zone that could rebut the assumption that you should know you're in the zone, but by your own admission there were repeaters which you saw.
The fundamental issue with your (mis)understanding of the signs is that either you're inside a zone, or you're not. It cannot be that there are signs and you are subject to them or not depending on how far you are from the sign, because that would render the whole concept entirely arbitrary: how could you determine how far from a sign is far enough? Given that most traffic signs impose strict liability, that would be far too vague, hence the start and of the restricted area must be clearly defined either by zone entry/exit signs, so you can know with certainty where you're inside the zone or not. Unfortunately while you might not have known any of this when you parked, ignorance of the law is no defence.
I would seriously recommend you make an additional representation as follows:
Dear Essex County Council,
Having taken legal advice, I now understand the entire zone is subject to statutory controls and the area where I parked is restricted irrespective of the distance to the nearest repeater.
Nonetheless I contend that the alleged contravention did not occur, because the signs fail to adequately convey the effect of the traffic order. I have now discovered online that I can actually pay £5 for a visitor's permit via the MiPermit app, even though there are no signs indicating this on the road. If the signs had informed me of the availability of a visitor's parking permit, I would have bought one at the time and the CEO would have found a record thereof on his hand-held device.
As the authority has failed to bring this key aspect of the traffic regulation order to the attention of motorists, the authority has not discharged its duties under regulation 18(1) of The Local Authorities' Traffic Orders (Procedure) (England and Wales) Regulations 1996, and it follows that the contravention did not occur.
Yours faithfully,
Of course the council will reject no matter what you say (you should always assume it will be necessary to appeal to the tribunal), but this is a contention that is at least arguable, while what you've put in your formal representation is not.