So, you parked here :-
https://maps.app.goo.gl/x6bYRrsnfyRSS37d8You parked in a marked bay, so it is your duty as a motorist to check for whatever restrictions may apply to that bay. You would do this by looking for a sign for the bay. There is more than one sign, so it appears adequately signed. The absence of a sub-code is not a big issue, provided the contravention is described correctly.
So did you go and look for a sign for the bay ?
The more you can tell us, the more we can advise on.
I'm afraid so far from your narrative, the PCN, and the location, you've got pretty thin gruel for an appeal at London Tribunals.