I've found a tree on ancestry that I am checking against the baptisms (pausing ocassionally to look on here because of the tedium) but I think in total if the tree is correct James and Elizabeth had:

James Sayer married Ann Platfoot
1781
William Sayer married Elizabeth Raper emigrated to the USA in the 1830s
1782
Susannah Sayer married Robert Newson
1783
Elizabeth Sayer married John Leeder
1784
Martha Sayer married ?
1786
John Sayer married ?
1787
Thomas Taylor Sayer married Elizabeth Wymer had some children she died and he then married Mary Elsegood Collins and emigrated to the USA taking the younger of Elizabeth's children and all of Mary's and then he had a load more when he got there.
1788
Robert Sayer married Sophia Swanton in London but then went back to Norfolk lost him thinks he also emigrated can't find him his wife or two children.
1789
Edmund/Edward Sayer married Mary Gall stayed in Norfolk
1791
John Sayer died age 23
1792
Samuel Sayer died aged 18
1793
Benjamin Sayer married Margaret Newson his sister Susannah's husband Robert's sister!
1797
Charles Sayer <----- my ancestor moved to Shoreditch, London with his second wife and all their children plus the children from his first wife Sophia.
1799
Joseph Sayer married Hannah Spraggs in London and had 9 children only 2 seems to have survived infancy Hannah died too and he married Sarah Sparkes.
1800


Edited to to put Edmund/Edward in I never did I forgot to and also the tree owner was quite correct Thomas Taylor Sayer and William Sayer both emigrated to the USA in the 1830s and created another Dynasty in St Lawrence County and Oswego County New York State. All these fact I have verified myself and they are true.