Really appreciate the prompt response, thanks for clearing the proxy issue up, as you say they have limitations.
As you point out you can't test the leaf colours under proxies, just a misunderstanding on the post.
The only small thing is to be able to test the leaves you have to plug the model into a forest pack scatter (for the map to work), so in each tree model file you have to create a fp scatter, a sun, a ground plane, test it, then delete the objects so as not to bloat the xref. The forest colour map doesn't render unless plugged into this method. I'm using Vray Next and maybe this isn't an issure with Vray 5?