So, I received your personal message but am still trying to figure out how to reply to it..!
So I have the parish record summaries for Cambridgeshire and they show 5 Sarah Charter (s) born respectively in Steeple Morden:
1784
1785
1807
1848
1849 a Sarah Ann
1871 a Sarah Jane
Do you have a date range but with these dates now you may be able to narrow down your search. let me know if this helps.