Only 4-5 flowering plants, but several more leaves present.
Early flowering time (December) and somewhat withered leaf tip suggests P. sphacelatum. Given the similarities between P. sphacelatum and P. tadgellianum, I would appreciate a double check for the ID.
Matt I would confirm P.sphacelatum for the following reasons. P. tadgellianum flowers are more crowded where these are more evenly spaced and the the petals of tadgellianum are relatively shorter to the sepals. The Callus of sphacelatum is wrinkled as is this one where tadgellianum Callus is smooth and again the labellum relative smaller and narrower. I am happy this is P. sphacelatum.
I am not sure I am either but using David's new book I feel a little more confident. There is a very interesting photo of P. tadgellianum and descriptions I am relying on. I have been having similar difficulties but feel I understand better now, but could well be wrong.