The flowers were larger, more orange-yellow, with the lateral sepals more heavily curved towards the stem. The stem was quite dark in colour compared to the typical nigromontana on BM. The shape of the flowers were more flat like a panda face, rather than gazelle-like. Quite different overall compared to nigromontana. I thought it wasn't a pardina (flowers larger than pardina), definitely not sulphurea, so the remaining species was semilunulata.
Thanks for the discussion and ID all. Maybe it received a bit more moisture and was happier considering it was in a relatively shaded spot on the south side of the mountain.