Thanks for the encouragement.
Here's an update, I want to play with the birch a little more, not too happy about the leaf colour and need to have a go at the bark tile, especially the displacement map at the branch roots. The GI on this one is 1 2, so there's room for improvement in the shadows, maybe need to make the stone gaps wider, but as there's going to be plants infront of the wall, I may leave as is. Oh, the wall is completely procederal btw. 50 mins to render on a quad core 2.66 XP32bit.