I have summarised these in a PowerPoint files and there are some interesting differences. For example P&C use habitat to differentiate between the three Fragrant orchids. It works a lot of the time but not always; yet I think there are some subtle differences in the leaf characteristics - occasional stomata or not, edge characteristics and probably seed size (or more particulary the ratio of length to width). This is an example of the presentation for one of the fragrants - chalk fragrant (Gymnadenia conopsea)
Quite what I do with the work when completed, I am not yet sure!