The mill that collapsed into the sea was part of the Isle of Man Board of Agriculture Fish Hatchery in the 1960s/early 70s. Its collapse over the cliff was reported in some detail at the time. The Board of Ag then moved it's operations to Cornaa.

Frances OS map at:
http://www.isle-of-man.com/manxnotebook/tourism/glens/wyllin.htm
shows the mill clearly