Earl Denman was my uncle (my fathers brother),both sons of John Dorrell Denman.If you go on abe books and search for "Alone to Everest",you can read his story.You can buy a copy very cheaply.
When Tenzing reached the summit with Hillary,he was wearing a woollen hat given to him by Earl.Both Earl and my father were born on Vancouver Island,but had to return to Heckington as young boys because their father was crippled with ill health.
John Dorrells wife was Harriett Allat from Swaton near Heckington.
I've just been looking at the Joseph you mention born 1773.His parents were Francis Denman and Hannah Cade.I was a bit thrown by the fact that she was born and they were married at Gamston,because I assumed it was Gamston,Nottingham.I've just discovered that there is a Gamston just south of Retford though and this must be the place.Joseph was christened on Xmas day,1773.