I've trawled thro' the actual Cadeby baptism records 1805-1825 and found no record of Sarah, but found 2 children born to 2 other single mothers, similar surname; perhaps she was a 3rd. She listed Cadeby as her birthplace in 1861 census Coventry. Records of Holy Trinity, Coventry for her wedding 06.06 1840 name her father as William, but I suspect this may be for social reasons, as she may not have known the name of her father, and I haven't found a suitably aged William at Cadeby for 1805-1820. She may have been born elsewhere and was told she was born at Cadeby.
Thanks again for your comments.