Good to hear from you. I am certainly willing to share my limited information about the Devonshires of St. Ewe with you. Contact me direct on firstname.lastname@example.org.
Robert Foote, who I was replying to, may have more information than me as he is a descendant of Admiral Sir Richard Devonshire, your ancestors younger brother.
My own Devonshire connection is from another part of Cornwall and also has a naval connection. My GGG grandparents were Lt. George Thomas Wingate RN from Stirling, Scotland and Thamzin (or Thomzin) Devonshire who I believe may have been the daughter of the shipwright John Devonshire from Maker, Cornwall.
Lt. G. T. Wingate was in command of the gunbrig, HMS Biter, when it was wrecked off Calais on 10 NOV 1806 and he and his crew were prisoners of war in Verdun until the end of the war. Amongst his crew on HMS Biter were Midshipman W. I. Devonshire andPetty Officer 1st Class John Wingate. These 2 are a mistery to me - were they related in any way to my GGG granparents or is it just a coincidence?
Thamzin, and their first born John, joined her husband in Verdun and they had 4 more children whilstPOW's in Verdun. All of the children born in Verdun came to live in Australia between 1830 and 1855. These were the artist/soldier Major Thomas Wingate (1807-1869), my GG grandmother Elizabeth (1808-1884), James (1809-?),and Lucretia (1813-1848). James went back to Stirling via Hong Kong after a period in Australia and I have lost track of him and his eldest brother John - the others all married in Australia and remained here until their deaths.