Thank you Xinia and Trish for your replies.
Regarding the Hartshorn connection, I will ask my mother for details, see if I can provide some names and birth years at least, see if those overlap with any of the Leicester Hartshorns.
Regarding Allerton, there seems to be some indication from legal records that the family property was in Bramfield in Suffolk, and that he had a son named Bartle who remained in England and was married there.
I expect that figuring out where they all came from within England will be difficult. My mother has used the usual birth, death, baptism and marriage records to get as far as she has gotten over here, and several of the ancestors have been verified as having been well established in the colonies prior to the revolution. The problem is that the records will show that they were born in England, who and where they married, when they died, the names and births of their children, but doesn't give any precise information about where exactly they came from within England. I do know that the New London, Connecticut area is where many of them seemed to take root here.
If I have names and years of birth, how would you suggest I go about finding birth records from that time period in England?
As I said, I'm a stone newbie. My mother's experience with this sort of thing has been only with obtaining records on this side, and my only experience is occasionally helping my mother find things on the internet. I know she has many books she has obtained from various historical societies.
I'm certain I have living relatives in England. Since that's where virtually all of my ancestors emigrated from, it would be very unlikely that I don't. I'd love to be able to find out exactly where the ancestors came from and see if it's possible to track down any long lost kin-folk.