The servants tunnel runs from the main house to the stables and has storage either side, including the coal bunker (see other panorama). Talk about "upstairs/downstairs"...
From Wikipedia page: http://en.wikipedia.org/wiki/Castle_Coole
At its peak, Castle Coole employed around 90 staff, both indoor and outdoor. The basement of the mansion was entirely the domain of the indoor staff, and accommodation for the outdoor staff was mainly found in the buildings surrounding the Grand Yard. During the early stages in the mansion's history when the main residence of the Belmore family was in Dublin, a caretaker staff of 5-10 servants remained in the mansion when the family were away. This may help explain the excellent condition of the mansion today; continuous occupancy prevented decay and may have helped prevent major disasters, such as fires.
As in many mansions, a hierarchy amongst servants formed. The Head Cook for instance enjoyed a two-room apartment above the warmth of the Kitchens. The Butler too enjoyed a personal apartment. A boot boy on the other hand had communal accommodation with other lower ranking servants.