An article by Judy Jowett in Silver Studies No 28, 2013 entitled "The Le Sage family of Goldsmith circa 1695 to 1812 " provides a large amount of extra detail on this silversmith.
Published by the Silver Sociey, back issues are available .
The Will of John Le Sage, goldsmith late of Saint Ann, Soho, was proved for probate on 23rd June 1759 and may be relevant (National Archives reference PROB 11/847/220).