Hi Simon,
Thanks very much apologies for the delay in replying, notice of your reply got buried in my inbox. I don't have that much more to add apart from the fact that before saw your posting I had also located the Greenwich burial and found the notice below via google books, the fact that in 1841 he was living in France ties in with your information that his second marriage was there. I have also got scans of an 1827 pamphlet he published 'Some Reasonings on the Distresses of the Poor, (agriculturists & Manufacturers)...' This describes the Bradford controversies from his point of view. There are also documents about this in the Wiltshire County Archives and letters from HCD to Lord Sidmouth the home secretary in the HO/52 series at the National Archives (available online for free). On the frontispiece of the 1827 pamphlet he describes himself as an 'architect and engineer'.
I guess you're aware that there is extensive Daubeny genealogical material in the London Metropolitan Archives (compiled by Sir Henry Charles Barnston Daubeny, a great nephew of our HCD) -- I've not managed to see it yet and doubt I will before submitting my dissertation. If you are able to and it contains any more biographical info on HCD I'd be interested in knowing about it.
Best wishes Paul --
ps if you want the 1827 pamphlet I'm happy to share.
London Gazette 1841 - p3255
Nº. is hereby given, that Henry Charles Daubeny, late of Windsor, in the county of Berks, but now residing at Boulogne sur-Aler, in the kingdom of France, has made application to Her Majesty's Attorney General, for leave to enter a memorandum of alteration in the specification of a Patent granted to him for his “invention or im provement in the making and forming of paddle wheels for the use of vessels propelled in the water by steam or other power, and applicable to propel vessels and mills,” as follow s. at the end of the first | clause of the said specification, to insert the words, “l also propose adapting the same principle to the common wheel," being to the effect, that his said invention or improvement is equally applicable to the present form of paddle wheels, or to wheels with horizontal floats, as to wheels with vertical floats, as described in his said specification.— Dated this 16th day of December 1841. Western and Son, No. 7, Great James-street, Bedford-row.