I presume you have Ethel's birth certificate, (therefore knowing her mum's maiden name).
Looking on 1911 census (free search, tweaking about). There is William MOORE, with a Mary Ann MOORE both age 30, In Manchester, with children Leah 5, William Jr 4, Sarah Alice 3, Edna 1. Married 1904.
I think you need to get that marriage cert!