Thanks for the feed back guys
The sparkles are caused by the fact that I'm not using a water plane, its mapped directly onto the ring world surface (no rendered planet in this scene). I couldn't get the plane to properly conform to the whole length of the fov, in the distance it displaced slightly less and subsequently "lifted" the river plane away from its desired position. Your right about the lack of displacement on the mountains. I'm working on a solution involving using a distance shader/merge shader to blend between near a far solutions. As "min/max slope" will not work consistently across the circumference of the ring I've avoided using min/mak slope to delineate surfaces much at all.
Next main work will be on developing a village, town and I may end up with a massive city on the , err, vertical horizon. (Hey these guys have no horizon!)
Yes the "Hedge" density needs upping and maybe a little more variety.
I don't expect to update much in the next few days, back up in London looking after the folks
Richard