Although, compositionally, I think the 16:9 crop is more successful, I'm beginning to think that the balance of light and tones is better in the 1:1 crop.
It was an 'end of day' shot, and therefore the light was fading, and although I could play with the levels etc in Aperture, and try and draw out more detail, this (as it currently stands) is representative of the scene as it was.
I might have a play when I get time, and post another version in due course.