Hi there, hope you are enjoying the site. It looks like cornwall opc have burials for St Agnes, there is a John Indean (senior) 7 Dec 1788 but nothing else fora John at St Agnes except John Indean's (snr) marriage to Mary Hill. However, there is this marriage at Perranzabuloe, 4 miles from St Agnes but it would make John 38 at the time so there may well be another John Indean!
John Indean 4 May 1794 Perranzabuloe marriage to Charity More. Then shortly after there is a John Indean buried 6 Sep 1794 Perranzabuloe.
From familysearch.org IGI there is a baptism at St Agnes 24 Jan 1788 Joanna Indean, parents John Indean and Elizabeth, so could this be your John?
Shirl