Hi there,
Thanks for the reply. I have worked it out using the standard set material action, and as I guessed I was missing something very simple.
I have included the explanation/method, if anyone is a silly as me in the future.
The material index option, within the set material action aligns to the elements in the mesh rendered, so by referencing the number that is relevant to the area you wish to change the material of you can control separate areas of the same object, in my case by using more than one set material action to repaint the desired areas at run time.
Cheers
Liam