I recently appealed a similar PCN and as in the GSV images in this case additionally found the signage defective.
Copied and pasted from my appeal text:
Firstly, the signage does not comply with the requirements of the Traffic Signs Manual, Chapter 3, Paragraph 16.1.4 namely: “All upright signs should face oncoming traffic as drivers need to be able to read them without stopping, otherwise they might be committing an offence.” The signage to the loading bay where our vehicle was parked is parallel to the road and therefore incompliant.
I've also sent the above email.