You state you descend from William Walch and Kate Sangwell. I have a William Walch who apparently was married twice and one of his wives was Kate. We do not know her surname. William was born in England about 1827. I descend from his brother, Thomas.
William and Kate had a daughter, Kate Ellen born in 1860.
Could this be your family? The foregoing is all the information we have on this specific line.