Thank you all for your ongoing discussion. In particular thank you
@stamfordman for going through the trouble of going to the location to take a photo.
I'm honestly at a loss for how I got it so badly wrong, I have good vision and don't normally make these kinds of mistakes.
Is me saying the sign hadn't been flipped over a poor defence? Would there be any onus on the authority to prove it had been done? The rejection letter says they do it "days before" an event, therefore any assertion that the sign wasn't flipped to match mode cannot be correct.
... surely that can't be true, because, if what they're saying is indeed the case, the implication is that, on the days leading up to an event, people are able to park without any restrictions whatsoever?
In these circumstances the best option might be the strategy of last resort, though I have come up with a few variations of it they all depend on the OP having some sort of mitigating evidence for the council to (fail to) look at.
The only thing I can come up with is just a screenshot of GSV which I saw before I set off. Or proof of purchase at the restaurant. They probably won't bother to look at either of those things.
If I wait for the NtO, appeal and then they reject it, will they re-offer the discounted rate?