One cannot 'rectify' a non-existent fault. However, it's most commonly not a question of existence vs. non-existence but, rather, a question of how reasonable the coding has been (given that it is subject to no 'rules, hence entirely down to the judgement/discretion of the inspector.Generally. Whether the fault exists or not, there is a document to say it does exist and that has to be rectified in some way.
We have seen many examples here (and elsewhere) - whether due to incompetence/bad judgment or attempts at 'work generation... for example, plastic CUs, CUs without SPDs etc. even dual-RCD CUs (and even, at least once) the absence of labels coded as C2.
I think that your use of the word 'fault' somewhat confuses the issue, even when the 'facts'[ about the installation are not in dispute. Do you consider the (undisputed) presence of a plastic CU may (at least in some circumstances) constitute a 'fault' that warrants a C2 coding?
I think most of us have agreed that T+E (well, any PVC sheathed) cable 'exposed to the elements' is not ideal, but we also know that it is generally OK for at least many years, if not decades - so 'unsuitable' is to some extent debatable. There are countless things (like car tyres, etc.) which are not regarded as 'unsuitable', despite their having a relatively limited in-service life.The only point I have against the span per se is the unsuitability of the cable for outdoors use. Others have said the same thing. As a regs catchall it may come under 'design' and 'workmanship' or whatever the correct terms are. No, unless there is a problem with it as mentioned above.
I don't dispute that - but, as I understand it, the OP's cable run is 2 metres, not "25m".25m of 3C 2.5mm² NYY-J from CEF ~£40.
Kind Regards, John