Hi Dijon
There is a baptism of a Charles Witt 23 January 1798 at St. Mary, Fen Ditton, parents Matthew and Sarah. Doesn't give Matthew's profession or any other details.
Not exactly Barnwell but close.
Looks like this Matthew Witt married Sarah Woollard at Fen Ditton by licence on 22 December 1795 both of the parish.
Selina