MYSTERY SOLVED
I should have looked outside the box... i (and my late mother) assumed that the William Hill who married Rachael Hutchinson in Ashbourne in 1816 was William Hill 1783, son of William 1760 and Mary (Tarrat).
William 1783 married Ann Taylor at Ockbrook in 1806 - so we assumed that when William Hill married Rachael Hutchinson in 1816 and had children at Ockbrook and Borrowash including my direct Great grandfather x2 Edwin in 1825, Edwins father was William Hill 1783...
William Hill 1783 and Ann went to live in London where they had several more children (Eliza was born soon after they married in 1806) and lead me wrongly to assume he was a bigamist leading a double life. This was made more compelling as William, Ann, Eliza, and their other children were on the 1841 census, as if William 1783 had something to hide.
That assumption was wrong.
Rachael Hutchinson married William Hill 1760, (1783's father) after William Hill 1760s first wife Mary Tarrat dies in 1815.
It was an easy assumption to make, as William Hill 1783 was only ten years older than Rachael, and when Rachael married William Hill 1760, he was 55, she was 22 !!!
So William Hill 1783 was my great uncle x3, not my great grandfather x3.... that is now thought to be William Hill 1760.