You can't add a SLMG class rating to a JAA PPL - you would need to get a TMG class rating - which you would get by doing a TMG skills test.
An SLMG class rating can be added to an NPPL.
To fly SEP aircraft you will need to RENEW your SEP class rating by taking an SEP skills test (renewal as opposed to revalidation because your rating has expired) with an examiner.
Once you have your renewed your SEP class rating and got yourself a TMG class rating, hours flown in EITHER will count towards the revalidation of both.
Confused?
