OP, you're not at Tribunal yet, there's the important formal NTO stage yet to be negotiated.
IMO, it's premature to concern yourself with adjudication, the question is whether you could succeed at the NTO stage and, if not, would the authority re-offer the discount again.
As regards the decision referred to, IMO there is nothing in this which would lead to the conclusion that the adjudicator considered the signage to be inadequate. Rather the appellant 'disputes the signage is clear', which is capable of many interpretations.
And as neither the appellant nor the council had put hard evidence in front of the adj the case was adjourned and determined because the council didn't respond. We could speculate what might have happened had they done so, but I don't see that this would be useful.
OP, let's try and nail one point: are you able to arrange for the location of all signs to be identified and plotted on a simple diagram? If not, then should you* decide to continue, you must put this to the authority in formal reps. Not just as a statement e.g. your signs are inadequate etc, but by posing a question which requires them to respond by identifying where these are and, if only at the gateway, why the council chose to place the barest minimum permissible** in theory, but insufficient in practice given the size of the area and situation in which the gateway signs have been placed.
* - are you the registered keeper with current DVLA details?
**- see s.13.10 of the Traffic Signs Manual which, although not law, is recommended practice and the authority may, and should, be challenged on this where there is a significant departure from its recommendations:
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/782724/traffic-signs-manual-chapter-03.pdf