Update
18 September: Informal challenge, in brief as was three A4 pages. 1. bay lines not compliant. 2. Signage inadequate. 3, PCN wording invalid.
29 September: Informal rejection. Nothing wrong, you contravened.
18 October: Notice to Owner.
21 October: Formal representations. 1. bay lines not compliant. 2. Signage inadequate. 3, PCN wording invalid.
13 November: Notice of acceptance. PCN cancelled because of 'a procedural error' (unspecified).
This demonstrates that it doesn't matter if an enforcement authority rejects your informal challenge you can make the identical challenge at the formal stage and have it accepted. Authorities wrongly reject many informal challenges because they know the public generally don't have the staying power to fight or the knowledge of an FTLA expert.