Just following up on original post.
Pleasant response from CASA, as per regs the validity is based on application date not issuance date.
Suppose fair enough - had it been assessed on application date (May 13th) expiry would have been + 6 months = November 13th....which is the current expiry of the recently received Class 1.
Obviously from my perspective a "bonus" month would have been nice, fortunately I didn't desperately need a Class 1 so the delay in assessment wasn't a deal breaker.
Cheers