have you tried taking one of the RGB channels for your black and white instead of just desaturating it? Go back to your original color and just look at the channels and see what you think. I think one of those channels would be more interesting in tone than just a desat.
Great shot though, I like it a lot. You may catch flak for the curve in your lense, (I've seen it done), but in this case I think it adds to the whole "church' theme.