JAR-FCL 1.005 (a)(5) Whenever a reference is made to aeroplanes this does not include microlights as defined nationally, unless otherwise specified.
The reason; some countries still don't require a licence to fly them, just like the UK originally didn't.
You could do a "microlight instructor renewal in it", but then you would have to pay to have a specific "microlight FI rating" put on your licence, and you would then have to do another test in an aeroplane that is not a microlight to renew your JAA FI!
Your choice!