There is an outside chance, William could have been married before. (or a relative) ... as I've checked with the Forest of Dean Marriage Licence and Bonds and there is this one
24 September 1782
William ELLOTS aged 27, labourer : residence: Westerleigh
Eleanor SMITH aged 28 - single woman
marriage by Licence
Sworn before Chris HAYNES to marry at Pucklechuch
and then the Bond copy
24 September 1782
William ELLOTS, residence: Westerleigh
Eleanor SMITH - residence: Pucklechurch
Marriage by Bond: He marks
Witness 1 : William SMITH of Pucklechurch and Harry SMITH
The groom and William SMITH are bound in the sum of £500 to marry at Pucklechurch.
Interesting.
Initial search: Can't find a death for Eleanor.
Children baptised in Westerleigh:
1783 Thomas Elliots to a Willliam
1784 Hannah Elliot to a Willliam
1785 William Elliot to a Willliam
1788 Hannah Elliot to a Willliam
1791 Joseph & Mary Elliotts to a William and Mary
1794 Mary Elliotts to a William
Not too sure if there all William and Mary. If they are it looks like William and Eleanor didn't have any children together. But interestingly, these dates do fit within the 1782 marriage and 1796 marriage.
Taking the age from the first marraige:
William Elliots baptised 1754, Chipping Sodbury to Samuel and Hester.
William Elliot baptised 1757, Horsley to William and Ann
Thanks for taking a look.