Well, you now have to decide whether to give up, or risk the full penalty at the tribunal.
I think you have some valid grounds to carry on: the explanation as to the location is wholly unsatisfactory because while there might be some internal council classification of zones, to the recipient of the PCN "zone A of Cranbrook Road" is essentially meaningless, it's not as it it says "zone a" on google maps or the ordnance survey, so the point is possibly stronger now than it was before.
Also they've conflated the concepts of service and delivery, which can win on its own as it's been held to be a procedural impropriety.
If you want to carry on, I'm happy to represent you at the tribunal.