So having said in the previous post that I was going to leave the water alone, I've gone ahead and changed my mind. After more thought I decided that the smooth surface was just way too smooth and almost any texture would be an improvement. So I took the approach that worked best in my experiments (a cotton wool bud to apply the Woodland Scenics Water Effects) and attacked the stream.
Once the water effects had cured I re-applied the extra details on the fall etc. and dry brushed on some ivory paint to highlight certain areas. It's not perfect but I think it looks a lot better than the very smooth surface. Hopefully you all agree?