In reality...
...as Whopity says it's down to the ATO.
However, being pedantic, if you hold an EASA licence already, that doesn't expire. The ratings and medical will, but the licence itself is valid for life. IF you hold a JAA licence with a validity of 5 years that has expired, the U.K. CAA will want to see a valid rating and medical alongside an application for converting it to an EASA licence. Old lifetime 'UK CAA' licences require similar should you wish to convert that.
You can only hold one EASA licence and your CPL will give you PPL privileges so the only thing required would be to attach the SEP rating to your CPL. You can still fly privately on your CPL with class 2 medical. As has been said, the ATO should devise a training plan for the issue of a class rating, (not a licence) based on an assessment that considers recency/competence/experience after discussing your requirements and looking at your documents. No great shakes.
HTH
DD