Ok, i've had success! The trimmer now starts and boy does she cut.
On advice from friends, I replaced the spark plug anyway and added some Valvoline Carbie Cleaner to the fuel.
I also cleaned out the muffler to improve exhaust airflow.
Started first time. I've just done the front yard and the thing just hums.
I guess the main method of how it was fixed was the spark plug. Even though the old one seemed to be sparking ok, the build up of a thick black residue over where the spark arcs inside the chamber must has been causing irregular ignition (or none at all).
Hope this helps anyone else having similar problems with their whipper-snipper.
Cheers,
Quinny
Australia
Quinny
December 2007