1. The PPL(M) has now become the NPPL with Microlight Rating.
2. You can add a SSEA Rating to a NPPL at a later date if you wish.
3. You can then upgrade your licence to a JAR-FCL PPL(A) should you so choose - but you will need to complete the training requirements stated in LASORS.
Download LASORS from here:
http://www.caa.co.uk/publications/pu...ls.asp?id=1191
It'll answer many of your questions.