Sorry for the late reply - this one slipped through the cracks. The witnesses at the wedding were 'Eliza Harding' (possibly the mother) and 'Isaac Clulee' (who turns out to be the Registrar on his day off).
I don't have the Death Certificate of Henry as it is only a possible match (but being the only one I found) and I'm not convinced that any extra information thereon would be of help. FYI, there was a Henry Augustus Harding who served as a sergeant in the Connecticut Militia (under Jonathon Wheeler) at New London and Groton from Jun 1813 to Aug 1814. He seems to have been married to someone named Phoebe Morgan in 1816. However, both parties were born in America. There is another Henry Harding from Great Marlow, Bucks. who served in some sort of militia at Eastbourne Barracks from 1808.
O what a tangled web we weave!