This seems a likely couple (John Jelly and Priscilla Jarvis/Jervis) from an online transcript of the Frome St John baptisms 1813-1821
http://www.gomezsmart.free-online.co.uk/7 Dec 1813 Benjamin Jarvis John & Priscilla JELLY Gentle Street Clothier
4 Mar 1815 William Jarvis John & Priscilla JELLY Keyford Clothier
8 Mar 1817 John Jarvis John & Priscilla JELLY Keyford Clothier
26 Dec 1818 Eliza Jarvis John & Priscilla JELLY Behind Town Clothier
17 Feb 1821 Priscilla Jervis John & Priscilla JELLY Butts Cloth dresser 8 Aug 1820
A John and Priscilla but different occupation.
1841 census HO107 942/12 folio 23 page 5
King Street Frome Selwood Somerset
John Jelly 50 Somerset Baker
Priscilla Jelly 45
John Jelly 10 Somerset
1851 census HO107 1932 folio 369
Palmer Street Frome Somerset
John Jelly 62 Frome, Somerset, Head Married Widower Baker
Frances Jelly 24 Frome, Somerset, Daughter
From FreeBMD up to 1851
Marriages Jun 1842
JELLY William Jervis Bath 11 23
Marriages Mar 1843
JELLY Jane Jervis Bath 11 21
Deaths Mar 1848
Jelly Priscilla Jervis Wincanton 10 449
Marriages Mar 1849
Jelly Eliza Jervis Bristol 11 169
Marriages Jun 1850
JELLY Edward Jervis Bristol 11 186
Edward's marriage details will confirm his father.
Regards
Valda