For what I hope is the final post on this thread, I appear to have sorted the problem, so for anybody curious here's what i did:
I stripped the rear indicator, removed bulb and disconnected bulb holder, i checked voltage, which was 12v with ignition OFF hence the indicator on constant. I then shorted the 2 wires together to trip the canbus hoping it would cure the fault when it reset itself. I then reassembled the indicator, but noticed the live connection on the bulb was hardly touching the bulb, so I bent the metal strip in further to make a good contact.
I reassembled unit, turned ignition on and its worked fine since, fault appears to be cured. simple cure to a baffling problem.
![Undecided :-\](http://forum.hexcode.co.za/forum/Smileys/default/undecided.gif)
If anybody has a rational explanation for this I would be interested.