No, the Little Grey Men involved do not include Michael Bloomberg. They are gnomes invented in the 1940's by Denys Watkins-Pitchford, who wrote stories as B.B. and illustrated them under his own name. A post on Nature, gnomes, and the power of story at Terri Windling's blog, Myth and Moor, put me onto his novel for children, The Little Grey Men. Actually, I had already recently encountered the book in Philip Pullman's Daemon Voices, which handsomely reproduces one of the illustrations (p. 256).
Pullman says of "B.B.": "In some ways he was a limited writer, but the honesty and passion with which he talks about wild things and wild places suffuses his best passages with a love of landscape, and specifically the English landscape, that is irresistible." True!