As already pointed out, the standard is that you need to have acted reasonably and in good faith presenting any information you aren’t sure about to your insurer for them to decide. Insurers have (or have been made to) accept that most people couldn’t tell if the wrong generation of alloys were on a used car unless they had a specific interest in the brand/model or something was obviously wrong, like the centre caps, colour or branding. Of course if you happen to have aftermarket alloys fitted and work at the UK distributor for the brand of alloys in question and that came to light, that may be a little different.
Remap wise an insurer would need a reason to check, your average car park ding isn’t going to justify it, what could cause them to ask questions is where the police accident investigation team perhaps determine excessive speed was an issue or the assessor notices something obvious like a remap company sticker on the back window etc.