Just a suggestion, but normally the fire would sit either in the centre of the room or in the middle of the longest wall. This would place it closest to everything else and in winter closeness is directly related to warmth. You've placed it in the worst possible place in terms of heating up the opposite corner of the room. We are talking radiation here of course because most of the heat just goes up and warms your ceiling.

Thanks Eanos, I see what you mean and will update it as I go.