There's no requirement for an authority to re-offer the discount provided this is done having regard to the Guidance. Their parking figures and experience might indeed lead them to conclude that it should not be offered - I don't buy into the 'at their discretion' nonsense which is prevalent because this calls for the exercise of judgement by officers but without the required detailed framework which would make decisions rational as opposed random.
But Members didn't have relevant data upon which to base their decisions- assuming this was confirmed by the Cabinet or council. They received a report which failed in its most simple task: it failed to identify the issues arising from the Guidance, in particular their scope, and develop rational arguments within this boundary.
The KC's opinion is at odds with the errors in the report(why is the KC always referred to as King's Counsel, did the author think that spelling the title in full added extra gravitas to the opinion??), I wonder whether they know how their opinion has been used?
I'll look at the two referenced reports i.e. Budget Options 2023 and Budget Setting 2024.
IMO, the report lacks reference to Legal Implications. Councils are required to take advice from their legal officers not external legal opinion, no matter how well qualified. I cannot find this reference which normally forms part of every report, for example:
Legal Implications - the Head of Legal Services' opinion is contained within the report or whatever.
Whether the above has any effect on the OP's dilemma will depend on how far the issue is taken i.e. to adjudication or not. An d this rather depends on photos!