I think one of the things that helps a lot of b&w shooters is understanding the old Ansel Adams Zone system... with particular attention to tonal range from 0 (pure black) to 10 pure white... If you can encompass the full range in a photo... the photo works, and should be your goal... shooting digital b&w is difficult because it doesn't have the same tonal range that film does...
I did a little adjustment in lightroom and nik tools, just to get a little more out of the clouds, was a bit tricky as I only had a small file size to use.
I like what you've done with it paul04. Just out of curiosity which sliders did you change in Lightroom to achieve the look of the edit you have done? Also what did you do in nik tools that couldn't be achieved in Lightroom?
I have Lightroom and as I shot it in RAW I was able to change the highlights to -100, lower the whites and blacks slightly and then up the shadows a little bit. You seemed to have been able to bring out the clouds even more though.
I like the overall shot, however comp wise I would have moved forward as not to get the gates in the shot, or move back to get both of them in. The shot does seem a little dark, but the second one is way over processed for my tastes.
Nik tools lets you add control points, so you can change different areas light or dark without affecting all of the picture, then I added a little more structure to the picture. this is nik tools with a picture I am working on.