Thanks everyone, that has been most useful. I see how that information all fits together, with the maps and CA database, sort of. The CA site has adits at 283412,637347 and 283439,637374, the latter thought to be backfilled, and a shaft at 283399,637063 which almost certainly has nothing to do with this as it does not show on any of the maps and may be very old. The adits have bearings of 119 and 123 degrees, and so will pass under the M74, maybe even into what was recently the Broken Cross opencast. They also explain the long structure parallel to and south of the main building, now disappeared, which would be as larker has described.
Curiously the existing long building is not on the 1955 (surveyed 1941) map. I think the surveyors caught the mine as it was being built, without all its facilities.
On Google Earth there is nothing where the shaft ought to be, near the electricity pylon. I suspect the CA have plotted the position incorrectly. Looking at all available satellite imaging I think it was actually at or close to 283404,637017, but the 6 inch 1864 map has two suspicious rectangles at 283425,637030 and 283426,637053.
There are a number of these long, narrow buildings with tower at one end in central Scotland. I will try to spot more of them next time I get a chance, and see if they relate to anything that the CA know about. I recall seeing one further south, beside the M74, where there should be no coal. I will get its position next time I pass.
I will try to get up there and take some pictures in the next few months, maybe once the worst of the winter is over, then see if it needs an entry of its own, or should just be added to the Auldton entry.