To the extent that the UK CAA are still responsible overall for air safety in the UK I would hope.
The NPPL is devolved to the NPPL Steering Group for licence issue and 'regulation' but I'd imagine they have no legal teeth to remove a licence nor have anything to do with legal action that might be taken against a pilot who breaches ANO regulations.
PART 31 POWERS AND PENALTIES
Revocation, suspension and variation of certificates, licences and other documents
228 (1) Subject to paragraphs (5) and (6), the CAA may provisionally suspend or vary any certificate, licence, approval, permission, exemption, authorisation or other document issued, granted or having effect under this Order, pending inquiry into or consideration of the case.
(2) The CAA may, on sufficient ground being shown to its satisfaction after due inquiry, revoke, suspend or vary any such certificate, licence, approval, permission, exemption, authorisation or other document.
As the NPPL is granted under authority of Schedule 7 in the ANO, and therefore falling under Part 31 for any licencing action, this gives the CAA every right to claim it as 'their business'.