Hi,
Your PPL(A) and a JAR SEP give you the right to fly a microlight - any type - without further training, tests etc.
Reason is that the ICAO definition of a SEP includes microlights - or rather, does not exclude them!
The NPPL is a UK licence and it changed from a NPPL (SEP) to a NPPL (SSEA) because of the international definition of a SEP.
The UK definition of a SSEA is basically a SEP with the exception of microlights!
So if you have a NPPL (SSEA) you have to look at the cross-crediting document on the NPPL website.
My three-axis microlight instructor has a JAR SEP and has never done any basic microlight training or tests. He has, of course, done the microlight instructor training and tests though!
(and revalidated his JAR SEP by flight test since he had no light aircraft flying hours in the past year!!)
Very best,
XA