Charles was always known as Duddridge, as far as I know, from 1841 until his death in 1909. I have looked for Charles birth elsewhere because on one census he claimed the neighboring village of Bicknoller as his birthplace, but he wasn't recorded there either. Stogumber was a pretty small place and it appears that Sarah Humphries' family were long time residents; I have found her parents and grandparents in the records there. The Duddridges were also long time residents and they account for a very large proportion of the population.
There were no Charleses of any surname christened in 1821 in Stogumber (nor in 1820 nor 1822) however, a Charlotte Humphries was christened in 1821 and her mother was a Sarah Humphries, with no father listed. So maybe this is Charles and some error has him recorded or transcribed as Charlotte. But I don't know if she was the same Sarah Humphries. It seems half the women in that time period were named Sarah. Too bad everyone in every line of my family was unimaginative in naming their children - I'd be rich if I had a nickel for every Mary, Elizabeth, Sarah, John, Wiiliam, George, Charles, etc.