Born in Reading, Stanley was first apprenticed to an house decorator whilst in his spare time painting with house-paint on card. First winning a Scholarship to Reading University, he further studied at the Allan Fraser Art College, Arbroath, Scotland. He travelled to America but returned during WWI to serve in the Armed Forces.

In Lamorna during 1923-1952, he was encouraged and heavily influenced by Samuel John Lamorna BIRCH, for whom he made frames (and for Stanhope Forbes and others) when finances were tight. He lived at Lily Cottage and worked often in the open air, and in the studio he built for himself (Bludor Studio).  He studied at the FORBES SCHOOL in 1926, and showed at NAG in Christmas Exhibition of that year. His titles included Sun Daisies, April Morning, Lamorna, etc. He also took pupils for lessons in the open air, carrying on the long-held plein air tradition.

A major treasure at Penlee House, Penzance is A Portrait of Stanley Gardiner painted in 1938 by the artist Richard Copeland WEATHERBY (Seal), that was shown first at STISA and then hung at the RA in 1945.  It depicts Gardiner 'who stands, legs astride, palette in left hand, brush to the fore, facing his easel with the Lamorna Quay in the background.' (D Bradfield)