I removed the starter motor today and cleaned it up, then removed end cap and removed the brushes mounting assembley. The arbour was black and glazed over and the grooves blocked,so i scraped the grooves clear and cleaned the copper arbour with a scouring pad until it was shinning.
The brushes looked to be half worn and original, so lots of life left,cleaned all the connections and refitted. Reconnected the battery and tested ..
All good

Engine cranked over nice and crisp and fired quickly.. I was that happy that i drove to tesco and filled the tank up £85

back to reality..
Also noticed all the mitsibushi logo on the starter and brushes, so must be good for another 100,000 miles.