In 1668 he was in Norwich, where he acted as one of three "heads and teachers" of a congregation of three hundred independents, who met for worship in the house of John Tofts, a grocer, in St. Clement's parish.
Fynch removed his flock to a brewhouse in St. Edmund's parish, which he fitted up as a meeting-house; and after the passing of the Toleration Act (1689) he secured a site in St. Clement's parish, being "part of the Friars' great garden", on which a handsome building was erected (finished 1693), originally known as the "New Meeting", but since 1756 called the "Old Meeting".
With the presbyterian minister at Norwich, John Collinges, D.D., who died 18 January 1691, Fynch was in close relations, both personal and ecclesiastical.
In accordance with the terms of the "happy union" (mooted in 1690), these divines agreed to discard the dividing names "presbyterian" and ‘independent’ and co-operate simply as dissenters.
"He was a man of most remarkable seriousness, meekness, prudence, and patience under that most calamitous distemper, the stone [...], mingled with the greatest zeal to do good to the souls of men; which qualities commanded the veneration of that great assembly, and kept matters in peace there."