Thanks to all for taking the time to respond.
In answer to your question BEagle, yes, I'm admitting that I haven't had a valid SEP Class Rating in my licence since June 2014...then again, neither have I flown since then. The reference I made regarding my IR(A) renewal in September 2013 was only to illustrate that I had met the criteria of having completed >1hr with an instructor in the preceeding 12 months prior to expiry.
Whilst a number of responses have said that the revalidation (by experience) endorsement must be made prior to expiry, I can't find anything on the CAA website that states that. Neither can I find any reference to it in an old version of LASORS. Can anybody point me to a relevant clause in anything official?
Cheers.