Brice,
My great-great grandfather was also a William Etherington. He was born abt. 1791 in Farnhurst, West Sussex. One of his children Samuel John Etherington was my grandfather (married to Martha Stevens). There were many Etheringtons born in Farnhurst (notice the different spelling). Also North Ambershaw/Ambersham, Lodsworth, and Hazelmere. But the most prevalent place seems to be LURGASHALL, Sussex.
Many Etheringtons were born there and some still live there today. Someone who may be able to help you is ***email address removed to stop spamming . He has a lot of Etherington information AND may be able to help you find your William.
***You could send the email address via PM. - Moderator