Michael S. found a pair of flower spikes a few days later about 9 paces from the first one the group of us saw on 18th June.
Then, when I went down to see them with him, I found another. So that's 4 spikes so far.
I have informed West Yorkshire Ecology, and am in correspondance with the Chief Ecologist at ARUP Consultants for the developer who has planning permission to build over this beautiful green space.
The Ecologist is talking about transplanting and the creation of an "orchid bank".
Michael has sent me an image of the new spikes he found, but I am unable to attach them to this. I am working on my old desktop as my laptop has broken down. This might mean me being a bit out of touch for a while.