Thanks for advice everyone. After much research went in for a supercharge MF55b24LS which has a 40 month warranty.
http://www.supercharge.com.au/superchar ... -mf55b24ls Wanted to stay away from autobarn as they quoted 159$ plus 20$ for install
So I drove all the way to a supercharge listed dealer centre road batteries (
http://www.centreroadbatteries.com.au/ ) in Springvale and wasn't disappointed. Danny did an old school test with one of those huge battery testers and confirmed my battery was a dead duck, in fact it didn't start the car after the test! He showed me some newton power options and then supercharge silver and the top end gold. Compared to autobarn, he quoted 130$ for supercharge gold, with the install included and I went ahead with the same!

Good business to deal with if you looking for an nc replacement battery.
Edit - quick tip, when you disconnect or replace battery, the dsc light stays on the mx5 nc. Simply turn your steering wheel full lock to full lock once and then turn ignition off n back on n the dsc light will be gone
