Wow, that's an amazing quantity of info - brilliant! I've just been adding it all into my tree.
I forgot to mention - there's another James Mansfield in the 1841 Colchester census, but I think the presence of Sarah Bunnell would make it 'our' James in the first example I found.
What I know about William Waynman, who married Sarah Cooper/Rayner:
Baptised 31 Aug 1713 in Manningtree, son of James Waynman and Mary (née Borham). James and Mary married on 30th Sep 1712 at Mistley, by licence (ERO don't have the licence allegation, sadly). William had siblings: Anna (baptised 1714 in Manningtree, and is a married woman with the surname Garwood in her father's will, but husband's first name not given), John (baptised Manningtree 1723) and Mary. On 23 Aug 1729, William Waynman son of James was apprenticed as a perukemaker to Samuel Browne of Colchester (as you've found). James ran The Thorn public house in Mistley, and when he wrote his will in 1750, he was a victualler in Harwich.
At some point, William married a woman called Eliza, and they had (at least) one child, baptised 13 Aug 1741 in Manningtree, called Eliza. I think this is the same Eliza Waynman who married William Winch in Fingringhoe on 5th March 1765.
As we know, William Waynman, widower of Manningtree, married Sarah Rayner, widow, at Fingringhoe in 1753. They have three children baptised in Manningtree:
Thomas - baptised 19 Feb 1755, married Mary Marsden in Colchester, dies in 1796 (his "good friend" John Whitaker Cooper is one of his executors. He also mentions that he has two children: William and Sarah. Also in this will, he mentions some property where someone called Miss Duvall is living - this is a surname I've seen before - one of the witnesses to the Cooper/Whitaker marriage in Ramsey is John Davall).
Sarah - baptised 4 June 1756. I would say her age is extra evidence that she is Sarah, wife of Samuel Farran, and then William Bunnell, mother of James Mansfield's second wife after the death of Mary (née Tiffin). (no wonder Ann Taylor was surprised with them all calling each other "cousin"!).
James - baptised 27 Dec 1758 in Ramsey, but there is a burial in Ramsey on 29 Jan 1759, for James son of William & Sarah Waynman - so quite who James Waynman, the Colchester lawman is, I don't know! (could he be a younger brother of William Waynman, rather than a son? If he was articled in 1766 - or perhaps the son of William's brother, John? How old were people when they were articled?).
William appears in
this bulletin from the East Anglia Postal History Study Circle, as the person who ran Manningtree Post Office, from 1741 to 1764.
A piece in the Ipswich Journal in 1761 mentions William Waynman of South Hall, Ramsey (which I think the Woodruffes or Woodthorpes eventually lived in) as a contact for information about poachers.
He died in 1762 (so either he's not the same fellow running the Post Office, or the date is slightly off, or perhaps his widow and or sons continued it for a couple of years) - there is a burial in Ramsey on 29 Oct for "William Waynman and his son" - it doesn't say which son. In 1763 there are two pieces in the Ipswich Journal, asking that anyone with outstanding debts owed to William approach Thomas Cooper jnr of Fingringhoe (his widow's brother, presumably). Thomas is William's executor, and William is described as being "late of Ramsey, farmer." I can't find a will so perhaps William and his nameless son with whom he was buried died in an accident together (but that usually gets a mention in PRs) or both passed away suddenly of an infectious illness, as wasn't uncommon back then, of course.
Apols if you already knew that!
Nottingham William does sound like a strand worth investigating, definitely.