Thanks for all the advise guys.

I will head to a GM (Holden in OZ) dealer this afternoon and see what they have. I doubt that they would have the product here, but no harm in trying. I thought I might try to measure the thickness of the head while I am at it to see if it has been shaved at all in the past.

Ever since changing the O2 sensor and the spark plugs, the plugs have stayed very clean. Just a light dusting of grey.

I'm not all that keen on the idea of an italian tune up. I will see what I can do by other means.