Hello Jacob,
The article which Len referred you to, written by R. Cunliffe Shaw in the Ramsey Courier of Dec. 24th.1952, is substantially correct. It was written from research (now held at the Manx Museum) carried out by two William Radcliffes during the 1920s. However there was some confusion between two closely related Radcliffe families, with the descendants of one family sometimes given to the other, and this error was repeated in an article by Constance Radcliffe who used the same sources.
Where Dr Shaw wrote "Another branch of the Sumner Radcliffes are those descended from John, the other son of Gilbert Radcliffe. This John died in 1674..." (wrong - John Ratcliff b.c.1635 [of Crot-e-Lough] died 1669 www.iomfhs.im/lawsons/twill/1669_005.html)
"leaving a will in which he bequeathed all his lands to his son John Radcliffe except a croft which he left to his wife and then to his second son Thomas" (no - left to eldest son John unless he died). Dr Shaw left out a generation here which led to the problems identifying exactly who belonged where in the later generations.
The Thomas Radcliffe who was in the Lords Survey of 1705 was the son of eldest son John Radcliffe b.c.1664, d.1701 [www.iomfhs.im/lawsons/twill/1701_010.html]. John d.1701 married Margaret CANNELL who died as Margaret KNEAL 22 Dec.1723. She married John Kneal after John Radcliffe's death, which apparently was why the Radcliffe researchers didn't find her will.
Their three children were Thomas b.c.1695/96, d.1732 [decree]; Jony b.c.1697/98, d.1739 [will: Joney Kinry als Radcliff]; Philip b.c.1699/1700, d.1762 [will]. All wills/decrees are on Brian Lawson's wills list.
Some of Philip's descendants were wrongly put in Thomas's family (e.g. the author of "Ellan Vannin"), but John Netten Radcliffe was correctly placed in the article.
I'm not sure what you are looking for with documents about this family. There are numerous wills, land records, etc. in the Manx Museum library, but they have all been pretty thoroughly picked through.
If you can give an email address I can put you in touch with a descendant of John Netten Radcliffe, for more recent family history.
Sue