Yay - sorted it.

I added a third skin and use it to control the gloss variable. Before it seemed to use some aspect of the normal map. (it can be a small map)

spec_bump_model_20.fx

Varying specularity can have a dramatic impact on the realism of a scene. Right now I need it so that my characters suit is highly specular, but the skin tones are not.

Thanks to Matt_Coles for the original code. I just bought a book on writing shaders - it is absolutely fascinating what they are doing in real time.