This seems to be the only COPP family (that I can see) directly related to Halberton:
John COPP (b. 1781 Portsmouth Hampshire) Ag lab, dairy man and retired farmer in Halberton census from 1841 to 1861 with wife Elizabeth ELWORTHY (b 1789 Halberton)
John COPP married in 1819 Halberton to Elizabeth ELWORTHY.
Their children baptised Halberton
Jane 1820
Elizabeth 1822
John 1824
Henry 1826
John James 1828 (edit to correct)
Thomas 1832
John COPP was a widower when he married Elizabeth ELWORTHY. He may have had other children from an earlier marriage.
Its possible that Elizabeth had an illegitimate son, from before she married, with someone named GORDON, who took on his step-fathers name Copp.
Whoever recorded the baptism of his last few children of John and Charlotte, knew of him as John JORDAN, and that he was using the alias COPP.