I like your image composition Paul, i do however feel that you have focussed on the green grass in the foreground, and the actual bales are out of focus somewhat :-(, maybe this was due to your choice of focus point or maybe it was an aperture issue. Sorry to be so negative but this is just my point of view.
How could you have improved this image? - simply moved closer to the bales and focused on maybe the closest one to your point of view, this would have given the image some foreground interest in focus, with following bales maybe slightly out of focus yet still keeping that moody sky and slightly less foreground grass for good measure.
The over all image is very good, so is your processing for my liking and the moody sky is great.
Daz