Thank you for your responses Spendlove and Colin, I didn't know that the 1842 census and marriage licence showed he originates from "elsewhere", so that helps. I'm favouring the Derbyshire connection because of the Christian names used in the family line, however....... for some reason his great grandson, also John Amos who was definitely born in Grantham, has told the 1881 census clerk (Leeds) that he originates from Mansfield Notts! and there does appear to be a John Amos born in Mansfield, but the date of birth is out at 1758.
Any idea how I could obtain a copy of the 1794 Wellingore marriage licence?