If a Class Rating in your licence has passed its validity expiry date, you may not fly as PIC on that class of aeroplane.
You will need to renew your SEP Class Rating by passing a renewal Proficiency Check with an Examiner; the licence may not be signed retrospectively.
Are you really admitting that you haven't had a valid SEP Class Rating in your licence since June 2014?
The fact that you held a valid IR(A) until (I assume) Sep 2014 is irrelevant; a Part-FCL licence has no expiry date, whereas ratings and certificates contained therein certainly do.
Wasn't this covered during your Air Law and Op. Procs theoretical knowledge study?