To make the black and white version, I added a b&w conversion layer, then adjusted the colour sliders - darkening red so the window frames were darker, lightening green so the corrugated paneling looked right, then adjusting the yellow slider darker till the grass looked right. I then added a masked curves adjustment layer in which the white point was moved left, and the line kept straight - this selectively emphasized lightening the lighter areas without affecting the darks. I brought out more texture in the windows, while avioding driving the cracked glass to pure white. I tried it on the paneling but it was too harsh so used a simple s curve on those to brighten the lights without pushing them to pure white, and slightly darkening the darks.
I then did my brown to black action which applied a solid tone adjustment layer, set it to colour, toned it down, then used the available layer adjustment blending sliders (by double clicking on the layer) so that the colour applied much more to the light tones than the dark. i then toned down the effect using a hue/saturation layer to taste.
My impression now is that I much prefer the new version, but that I might choose to work further on the right sided windows so that the lighter areas better balance he left side of the picture - but first I'll live with what I have for a while.