I've been looking at Ellough records available on line. There are two baptisms to daughters of Nicholas and Elizabeth, they are Mary in 1715 and Sarah in 1717. But the parents can't be the Nicholas and Elizabeth buried in Ellough in 1795 and 1792 respectively as they would be much too young, years of birth 1705 and 1707. So there must be an older Nicholas who married another Elizabeth, possibly parents of Nicholas 1705, and Mary and Sarah are his younger sisters.
i've also found an apprentice record for a Thomas Ayres apprenticed to Nicholas and William Ingate blacksmiths of Willingham dated 1778
So now my theory is
Nicholas Ingate married Elizabeth X in early 1700s, they had children William (our William who became a blacksmith in Kirby Cane), Nicholas 1705 (who became a blacksmith in Willingham), Elizabeth (who married James Waters wheelwright of KC), Sarah and Mary (bapt in Kirby Cane). Nicholas 1705 (bondsman on our William's marriage licence) married Elizabeth Sherman in Sotterley in 1741 and they had children: William who became a blacksmith in Willingham (and was master jointly with his father to apprentice Thomas Ayers) and Nicholas jnr who was apprenticed to James Waters his uncle by marriage as a wheelwright. Nicholas jnr was witness on his brother's marriage record. There is a transcript of a gravestone for a William Curtis Ingate s/o
William Nicholas and Ann buried 17 April 1786 who died in his ninth year. The dates would fit as W C Ingate being the son of Nicholas jnr and a wife whose maiden name might be Curtis. Also mentioned are Nicholas and Susannah who died as infants - possibly also Nicholas and Ann's children.
I need a few baptisms and marriages to support this theory though!