This looks like a new colony. The original sighting of A. collinus was at the top of a gully on the eastern side of the mountain, but this looks like a new location.
Good to know Tony - thanks. It was in an area with quite a lot of P. nutans as well. It kind of felt like the fading A. collinus were gracefully handing over the baton to the up and coming P. nutans :)
I'm not sure. The flowering times of the two species do overlap. The dorsal sepal does look somewhat narrow, although not so much in the photo below and I thought this might be due to the angle at which it was taken. The other features to look for are whether the lateral sepals are crossed and whether the petals are held away from the flower.