G,
I understand that you may have had some involvement in scribing the documents mentioned ;-) The rules are not different and the ANO still applies. However, the BMAA Guide to Airworthiness Procedures and TIL 020 further extend the privileges of, amongst others, PPL holders who are owners or part owners to certify maintenance action which under other regimes would require a LAA Inspector or LAE. It would be incorrect to describe this as Pilot Maintenance which has a particular definition under the ANO.
The rules on NPPL(M) validation are not the same as for NPPL(SSEA) or JAR-PPL(SEP) are also different [5 hours in 13 months, stamp in logbook from a microlight R examiner.]
The rules on NPPL (M) revalidation are the same as for NPPL (SSEA) as they are contained in the same section of the ANO, Schedule 7. The 5 in 13 rule to which you refer is for the old PPL (D) and PPL (M). This can be signed by
any "Revalidation" examiner. Of course, a sensible recommendation to all examiners is to know what you are signing for as I have seen some remarkable stuff, including an FAA instructor's signature on a SEP Certificate of Revalidation following a FAA BFR in the USA, and even more recently a licence with no CAA stamp over 4 years old where the SEP had already been revalidated twice.
G, I agree with your statement about needing to know your stuff if you're teaching on it though.
HTH