Thanks for all the comments, especially the ones regarding the building blending in with the background. I've certainly taken that on board now! Light on the day was not good and with basic editing....
This was my first entry into a challenge and although not high scoring, I found it quite exciting watching the scores and comments come in and I even got a few eights, which is encouraging. I've now joined and become a full member and look forward to more challenges.
It may have been your intention to photograph this in such a way that the subject blending in with the background, but for me it makes it hard to see certain aspects of the shot. I would have preferred a greater dissociation of the two elements.
Maybe you were going for this, but It's hard to differentiate the building from the horizon because they are at the same level in the shot--maybe taking the shot from a lower position would have helped?
the roofline of the pillbox runs into the skyline, making the composition rather flat. If you had taken the photo from just a little lower, so that the pillbox would stand above the trees, it would have been more dramatic.