There is a bapt. of a William Downe(sic) 1773 Crediton, son of William and Sarah Downe (sic).
Wife Mary Frances Bedford bapt. 1771 Crediton.
Mary buried 1831 Islington, London aged 58, but cannot find a definitive burial for William which assume would be in London rather than Crediton.
There is a tree on Ancestry that has the death date as 1850, but cannot find this on the GRO index.
Also on this tree, they have a William bapt 1794 marrying Mary Frances Bedford in 1802. Have checked this baptism and this William was born in 1791 so could not possibly have married in 1802.
Sally