I wish I had got a copy of the episcopal will, it looks like it would solve a new problem: it must be a different William, whose c.1811 burial I can't find either! There are quite a few William Corjeages and I think I have accounted for all but two:

William son of John Corjeage & Christian Bodaugh Bapt Apr 13th 1736 KM (reg)
William son of John Corjeage & Christian Cannon bapt. Apr 16 1752 KM (reg)

Meanwhile I have two burials I haven't identified yet:

CORJEAGE, William, Mic, 8 Apr 1751 (Lawson) - Corjeage, William, son of John, B, Killey [not much help, but perhaps a child] 08APR 1751
and
CAVENDISH, William, 35, Bra, 31 Mar 1916 (c162 GR: DDD) [can't remember what that means, but too late anyway]