I think this is your John.I have reason to believe that the children of John and Sarah (Bentley) Hanscombe were toddlers when they were baptized, rather than infants, and that would allow for a John, b. 1820, to have been identical with John Bentley Handscomb, bapt. 7 June 1824.
Here's how I think the whole family looked (and notice the use of the names "George", "William", and "Alfred"):
JOHN HANDSCOMB of Bishop Stortford, Herts, m. 5 November 1800, SARAH BENTLEY.Their known children:
1.ALFRED HANDSCOMB, b. c.1802.He had a first wife, Elizabeth, and by her, one son, Alexander (chr. 24 July 1825).He then m. 2nd, 16 Oct. 1830, Eliza Fairhurst.By her, he had three more ch.:John (chr. 19 Dec. 1835; died young), John (chr. 18 June 1837), and William Frederic (chr. 12 Dec. 1845)
2.CHARLES HANDSCOM, b. c.1806.He had wife, Eliza, and one known son, Alfred (chr. 28 Oct. 1843).
3.GEORGE HANDSCOMB, b. c.1810 (chr. 21 May 1813).He had wife, Eliza, and seven children:Emma Louise (chr. 11 Sept. 1836), George John (chr. 4 Mar. 1838), Sarah (chr. 25 Mar. 1842), William (chr. 7 Feb. 1844), Albert (chr. 1 Mar. 1846; died young), Frederick (chr. 6 Aug. 1848), and Albert (chr. 28 Mar. 1851).
4.MICHAEL HANDSCOMB, b. c.1812 (chr. 6 Jan. 1815)
5.ANGELINA HANDSCOMB, b. c.1815 (chr. 24 May 1818)
6.FREDERICK HANDSCOMB, b. c.1818 (chr. 26 Feb. 1823)
7.JOHN BENTLEY HANDSCOMB, b. c.1820 (chr. 7 June 1824) ... your John???
8.KERENHAPPUCK HANDSCOMB, b. c.1820 [likely twin to John] (chr. with John, 7 June 1824).
All of the children of John and Sarah (Bentley) Handscomb were christened at St. Michael's Church.With a couple of exceptions, most of their known grandchildren were christened there as well.