Hello Stigs
Your info on Thomas Stiggers confirms that there must of been two Joseph Mouchet/Mouchat's living in Lambeth at the same time. The burial in 1848 must of been the other Joseph Mouchat and not your Joseph who married Harriet King. I don't know when your Joseph died. I can't find your Joseph & Harriet on the 1851 census either.
I am not sure how your Joseph is related to my Mouchet family. Your Joseph & Harriet and their children are living with my Mouchet family in the 1841 census. My Mouchet family in that census are mother Sarah and her three children Sarah, Henry, Caroline. Mother Sarah was born about 1792 in Cripplegate, London. Father Samuel Mouchet is not on that census. I presume he died before 1841.
I have not found a baptism, marriage or burial for father Samuel so far. I have not got any further back from him in the Mouchet line. I do however believe that our Mouchet's are related to Henry Ann Mouchet mentioned in a previous message in this thread. Henry Ann Mouchet's family came from Colombier, Neuchatel, Switzerland.
I would like to see those Mouchat birth certificates. I will send you a personal message with my email address.
Pilgarlic