The method I ended up using was something fairly crude but effective, a mix of zbrush - meshlab and a nice relaxed unwrap:
Taking this mesh into UDK and vert painting it with different tiling rocks I got a result like this:
The second big challenge was the water, initially I tired some tesselated water but the reflections didnt come out too well as they werent based on the tessleated mesh but instead the low poly. So i went with a more than likely overly complex water shader with additional scrolling wave planes:
Anyway, here is the scene as it stands at the moment:
I will update this in the near future!