Hi, I probably only have the same info as you on John Sargent.
I am descended from his son Philip born 17.3 1780.
I have spent a lot of time researching this family and have discovered there are no Sargents in Icklesham previous to John.
But there is a generation gap and Sargents appear in Winchelsea from 1685 till 1820.
One of the Winchelsea descendants was a Lewis Sargent, born 1.1.1809 son of William Sargent born 21.6 1785,son of William Sargent born 1755 (all 3 being listed as Miller for a profession). My grandfather used to talk about Lewis Sargent as being a family member who owned the mill at Hoggs Hill, Icklesham and I also have a photograph of Lewis in my family album.
But so far have never managed to find the connection.
John Sargent married Mary Crassingham in 1766. I have a copy of a removal order for her from her parish to Icklesham (because she was already pregnant) and John had to marry her.
I have many other records of this family if you are interested.
I would be very interested where you got the date 1745 for John's birthday?
Looking forward to your reply.