Hi Stuart, the over-cast lighting is perfect for this scene. The water has a nice blurred look to it at the chosen shutter speed too, but I also see a significant amount of cloning and repeating patterns along roughly one third of the left side of the composition that really does not work at all.
Hi Stuart, this is much more pleasing to look at without the cloning. The overall composition would work better if the waterfall was positioned more to the right and possibly even better as a horizontal assuming there are no distracting elements to affect a horizontal orientation. If the waterfall is nearby to your home you may wish to revisit and try out several various compositions in both horizontal and vertical. It does look like a lovely spot that I think you could work a little more for a very effective composition.
If you are pushed for room with your current lens set at this location maybe you could try stitching together multiple images? Its not so difficult if you haven't done it before.. Another portrait format image stitched on to the left of the posted image would make all the difference here i think. More Pixels too..!!