I have found that my Gladwyns come from Essex. In the 1861 census for South Stoneham in Hampshire, the following family live on the Floating Bridge:
George Gladwin, 53, Toll collector on Itchen River Bridge, born in Woodham Walter, Essex Henrietta S. Gladwin, his wife, 49, born in Great Burstead, Essex Henrietta Gladwin, their daughter, 23, born in Great Burstead, Essex Joseph Gladwin, son, 21, Bookseller, born in Little Burstead, Essex Eliza Gladwin, daughter, 17, born in Little Burstead, Essex.
Woodham Walter is 26 miles from Harlow.
Although you cannot find any William Gladwyn in your family, perhaps the spelling of Gladwyn with a Y (the correct spelling of my family's name - it's only spelled with an I on the census) and the close location means that the families are somehow connected. It's interesting stuff.