Some IDIOT with a grinder (me) cut into the axle shaft while attempting to removing the old bearing. I have been advised that it would be unwise to use it. I am now searching for a replacement passenger side axle for V6 Capri. If anyone can help me out I would be grateful.....

Rear axle shafts, or half-shafts as some call them, are a universal fit, that is, left and right are the same size, length, etc. I have 3 here in Melbourne, but surely someone up your way in Sydney would be able to help you out there!

Thanks Foxy
 
Just be aware that not all rear differentials have the same length axle on the left and right side and I have found out the hard way that even the body style of a specific model of car can affect the axle length.
 
The reason I asked for the passenger side specifically is that I was always told as an apprentice mechanic to never employ a used axle on the opposite side as to which it had already been used in service. The reason being that during its service life it had been subject to a twisting force (torque) and that using the axle on the opposite side would twist it in the opposite direction causing it to break much more easily. I dont know how true this is but it was what I was taught by my TAFE teachers and was in the text books.
 
Is this true or just myth?

You should be ok.  Parts book shows same part number for both sides. 
 
I cant think of any engineering reason to suggest that reversing the direction would have any affect on the fatigue life, or breaking stress of the shaft.  I would guess that they would have been designed for infinite fatigue life for safety reasons and unless dragged, would never have seen stresses anywhere near the yield limit.