Thanks folks, @Ulco, not too sure, could be the obj, it has no mtl file with it, so does that mean that the normals have not been calculated?
Do I have to run this through Blender(or similar) to create a mtl file and normals?
Could also have been caused/worsened by render quality settings??
I will investigate further, may need some subsurface smoothing in Blender, but I don't want to lose the integrity of the object's form....
@Bobby, cheers for the heads up, about the grass, I will check that one out!
Cheers
Jason