This one is H muticus, which often occurs in typically low numbers in these kinds of habitats around Canberra. Labellum appendage too pale for H bicolor which is properly black (overall flower shape a little different too).
I thought muticus at first, but I thought the shape was closer to bicolor (when compared to illustrations in the ACT guide). Hearing from you that muticus grows in those conditions is quite helpful as I thought that this genus only grows in open field conditions.
Yeah, H muticus is the dry woodland and mallee species, most of the others are open grassland species (although I think H bicolor in Vic grows in woodland too).