No need for an official response.
You can fly a three-axis microlight on a non-NPPL light aircraft licence. No differences training required, no ratings, no sign-offs in logbook. (Although training extremely highly recommended.)
Indeed, we have a microlight instructor here at Strathaven who doesn't have a microlight licence - he has an EASA SEP with a microlight instructors rating attached.
So that must be some sort of official proof!
(there was a thread here on Pprune about eight years ago when he was told by the CAA and the BMAA that he had to get a microlight rating, and thanks to ppruners - to whom I offered up a #100 donation - the CAA had to back down and issue a FI(M) on his then JAR SEP>)
We have also had a Citation pilot (and light aircraft FI) teaching on our microlight C42.
So there are quite a few people with illegal licences flying around who we have taught with instructors who don't have microlight licences!