For all those who have helped me with this query, with many thanks to Boo who sent me copies of James Martin's Will yesterday, here is an update. I haven't completely transcribed the six closely written pages or so but essentially James Martin left bequests firstly of annuities of £20 to his personal servant David Clark, as a recognition of his "kind attention during my long illness" and to Christopher Martin of Thornton-le-Clay.
Then half of his estate in trust with to Ann Hetherington or Etherington (and her heirs) and the other half in trust to Roger Martin of Scorton near Catterick, laborer (and his heirs). He was very careful to exclude Ann's husband who was also described as a laborer (didn't even know his first name in the Will) from receiving the legacy and made provision for Ann to receive it in cash, covertly if necessary.
"one half of the said trust during the life and unto the day of the death of Ann the wife of ... Etherington otherwise Hetherington of High Coniscliffe in the County of Durham Laborer before marriage to him called Ann Martin from time to time to come in and be received with her proper hands or unto such person or persons as she whether covert or sole and notwithstanding her coverture by any writing under her hand to the intent that the same may be for her sole separate and peculiar use and disposition and may not be subject to her own anticipation or alienation or to the debts control disposition or engagement of her present or any future husband".
Though the husband continued to receive a life interest if he survived Ann, after his death or hers if he predeceases Ann, her children inherit her share. Her children (not named) also received cash sums of £250 each under a later codicil made on 10 October 1849.
In four codicils he makes changes to personal bequests, at one stage his gold watch was left to Roger Martin, in a later codicil he left it instead to his solicitor who witnessed several of the will and codicils!
He originally leaves his personal effects, plate and goods to his unnamed wife for as long as she remains a widow, after which those also revert to the trust, though he later modifies this so that she cannot sell them, requiring inventories to be kept by his trustees! He specifically states that he makes no other provision for her in view of her marriage settlement, though later he changes this to give her a lifetime income.
He specifically asks his trustees to complete the purchase of certain copyholds in Gate Helmsley which he had already agreed to buy from a Mr John Cook and also to grant a lease of Gate Helmsley Retreat to Mess'rs Laysock and Jackson.
At no point does he name his wife (though we know it was Anne) or explain the relationship with the others named in the Will. The last Codicil, dated 10 Sept 1850, is witnessed by William Reed, a Surgeon of York so presumably he could witness that James Martin had mental capacity at that time. The Will and Codicils were dated between 16 June 1848 and 10 October 1849, the last Codicil which left funds of £500 for a school in Gate Helmsley. The will and Codicils were proved on 10 Sept 1850.
One of the things which struck me most about this complex and frequently changing disposal of what must have been a reasonably substantial estate was that in each of these James Martin did not sign but made his mark - he was illiterate, this apparently successful businessman, and could not even sign his name!
This does not explain the exact relationships between Ann Hetherington and James and Roger and Christopher Martin but I am planning further research with this information which may help there. That marriage settlement between James and Anne could make interesting reading, too. Nor does the will explain how George and Jane Burn came to be running the Retreat on 31 March 1851, so soon after James's death when George Burn described himself as the proprietor at that time. But it certainly establishes that there was a link and a close one between them.
Many thanks to all those who have helped me so much, I hope you enjoy seeing what has emerged since which confirms much of what we speculated. And my friend is delighted with what I have found out for him.