You Aussie and Brit fellas are very lucky, in the U S all our fuels are 10% ethanol, even the premium 92 octane now has ethanol in it, and the highest octane rating is 92. The fuel starts going bad, without STABIL in it, in 3 weeks. I am also firmly convinced 1/2 oz. per gallon of Marvel Mystery Oil, makes it safer from degrading also, plus getting some minute amount of upper engine lubrication.
RGS-BILL