In the context in question, I think we only really 'hear that' from you . The rest of us understand that such questions are virtually never going to get anywhere near a court.We hear the phrase let the courts decide, and that is how British law works ...
However, even if a case did 'get to court', I don't think that would help. A court is, itself, not competent to rule on technical questions. If the laws and regulations did not give an explicit answer to a disputed technical question, the court would have no option other than to look to expert witnesses - and, just as with the discussions we see here, they would end up with two groups of expert witnesses presenting opposing opinions.
For example, if the issue being tested was whether or not a plastic CU under a staircase should be given a C2, I would expect that both the 'prosecution' and the 'defence' would be able to produce equally apparently 'authoritative' expert witnesses to support their side of the argument - so, short of 'using a pin', I'm not sure how the court would "decide".
As I said, I think the only answer would be to (as far as is possible) produce 'explicit rules', leaving as few grey areas as possible which required case-by-case individual judgement/discretion.
We certainly do now have a dichotomised situation. For owner-occupied properties, the situation remains as it always was, that a property owner is free to act upon or ignore the findings of an EICR, whereas for rental properties an EICR now has legal teeth, with potential substantial financial implications for landlords.Some one in government needs to state what is permitted with rental property and not try doing it on the cheap by linking to BS 7671.
However, I don't think it is sensible or practical to expect the government to produce its own set of 'regulations' specifically for rental properties - since the implication of what we're discussing is that any such set of regulations would presumably have to be even more detailed than BS7671!
However, given that it appears to be BS7671 that had invented 'the codes', I would think that it could go at least some way to offering at least guidance as to what non-conformities should be given what codes. As things stand, as far as I am aware there is literally only one such bit of guidance - namely that the absence of required RCDs should be given "at least a c3"!
Kind Regards, John