OP, thank you.
Clearly, CUP are one of a small group of BPA members which does NOT issue PoFA-compliant notices(it's not obligatory)..which is why the 'relevant period' doesn't apply. What they do is send out these speculative invoices with random legal references and hope to catch the unwary. They haven't posted an otherwise PoFA-compliant notice late, they're not looking to engage PoFA at all and therefore the only person who could be liable is the driver, hence repeated references to you excluding anything from your posts which could be used to deduce/guess at that person's identity.
Now that we know their MO, DWMB2's draft is more wide-ranging than mine and now I would be tempted to go further and perhaps this might be developed.