No wonder people are confused....
There is so much incorrect nonsense on this thread that it is difficult to know where to begin.
Anyway, the PA28R may be flown using an NPPL until
7 Apr 2015.
The SSEA Class Rating was originally an NPPL Class Rating for a specific category of light aeroplane,
not being a Microlight.
Want to fly a Microlight? Get a Microlight Class Rating.
Want to fly an SSEA aeroplane? Get an SSEA Class Rating.
Want to fly an SLMG? Get an SLMG Class Rating.
Simple enough. But then someone at the CAA decided that Microlights could also be flown using SEP Class Rating privileges, provided that differences training (more correctly, conversion training) had been undertaken. There was no recency requirement for flying Microlights and any such flying wouldn't even count towards SEP Class Rating revalidation.
Meanwhile, we finally got shot of the stupid 'rolling validity' nonsense (which EASA have now reinvented for their LAPL

) and introduced consolidated NPPL revalidation requirements for holders of more than one NPPL Class Rating. Which are simple enough to understand and quite reasonable.
Then came the ORS4 saga. The CAA's original idea was to allow people who had lost their Class 2 medicals to carry on flying until they either regained their Class 2s, or the licence expired. Regrettably, some barrack room lawyers abused the system and as a result, the scope of the exemption was reduced.
Regarding the LAPL(A), I am currently working with the CAA on credit for Microlight pilots. As the UK has a robust Microlight-to-SSEA conversion process, that should be the starting point, followed by NPPL(A)-to-LAPL(A) conversion, with due credit for requirements common to both. It won't be in the first issue of CAP804, but we hope to sort it out by the second.
Regarding aircraft such as the Ikarus C42 which nudge the boundaries of the Microlight Class Rating, remember that it is a
Class Rating, not a C42 Type Rating.