Thanks to the information you posted, I was indeed able to verify that William and Rachel are the parents of Margaret Dinning. For anyone interested in this family, here is what I've found.
William Dinning m. Rachel Granville 20 September 1812 in St. Thomas Church, Bristol. They had three known children:
Joseph Strong Dinning, chr. 27 June 1813 at Temple Church, Bristol; Margaret, b. about 2 January 1814, chr. 5 May 1816 at Temple Church, Bristol; and Rachel Ann, b. about 1817, chr. 29 August 1824 at St. Peter's Collegiate Church, Wolverhampton, Staffs.
William d. 18 June 1857 in Wolverhampton; his wife Rachel probably died before 1851. I believe William's parents were Strong Dinning and Margaret Watson, who immigrated from County Armagh, Ireland to Bristol around 1809. Strong Dinning owned a grocery in Bristol on Temple Street in the early 1820s. Other children of Strong Dinning are Robert, John, Catherine (m. Robert Parker), Sarah (may have died young), and possibly Anne (m. James Brown).
Joseph Strong Dinning was alive in 1833 to serve as a witness to his sister Margaret's marriage to George Anson in Wolverhampton. I believe he may have worked as a law clerk in London in 1861, but have no leads other than this.
Margaret m. George Anson 30 June 1833 at St. Peter's Collegiate Church, Wolverhampton. They had 15 children, immigrated to America in the late 1840s, and settled in Quasqueton, Buchanan County, Iowa. Margaret d. 15 April 1896 in Rolla, Phelps County, Missouri, where she was living with her eldest son, William George. She is buried in Quasqueton with husband George (d. 1889), and eldest son and his wife.
Rachel m. George Leadbeater 19 April 1835 at St. Peter's Collegiate Church, Wolverhampton. They may have moved to Wolstanton. I have no other information on this family.
If anyone has information on Strong Dinning and his family, or any Dinnings from County Armagh in the 1700s and 1800s, I would love to hear from you.