My William (apparently b. c. 1796) appears in the 1841 census in Drivers Passage,Cambridge. He is married to Hannah (b. c. 1792? in Ireland). They are the parents of Luke, b. 1818, Susan, James, John, Robert, Hannah, Eliza Ann, Sarah and Henry. He is a gardener. All the Williams I have found that might be him,seem to have been born in Ely. He may have had a brother named Luke, b.c. 1791. Do they tie in with any of your Haylocks?