I see that these names don't feature on the IGI's
Are you able to access the LDS films,
I see there are some Bishop transcript but not the years specifically you want
Baptisms, burials, 1676, baptisms,marriages, burials, 1677-1678, 1680-1684, 1691-1694, 1698-1700, 1704-1706, 1714-1728, 1720-1721, 1728-1732, 1731-1737, 1741-1761, marriages, 1763, baptisms, marriages, burials, 1761, 1804-1805, 1762-1763, 1765, 1764, 1766-1770, 1772-1773. FHL BRITISH Film
90241 Item 1
http://www.familysearch.org/Eng/Library/fhlcatalog/supermainframeset.asp?display=localitysearch&columns=*,0,0
Have you had contact with the Callington OPC
http://www.cornwall-opc.org/Par_new/a_d/callington.php in case she has the records awaiting transcription
Also have you looked at any of the HALLETT wills for the 1700's early 1800's that may have some family clues, there are several listed for other areas
Good luck
