This strays slightly outside my sphere of knowledge in that your primary issue concerns the enforcement process of a CCJ, and the application process for help with fees in relation to a set-aside, rather than defending a claim in respect of a private parking charge.
It would be helpful get some background to the case, for example to know what information he submitted in support of his set-aside application (a redacted copy of the N244 might be useful). The fact that HCEOs are involved suggests a higher than normal amount owed - more than one PCN?