Hi findmypast search of 1921 census for the same address, 181 deykin.avenue, shows a mary williams (wife) living there with her husband James Thomas Williams. Both aged 42. Details show James as born St. Just, Cornwall, & Mary born in Ireland (think it says Templemore). James is listed as com.builder, GEC. (Presumably commercial builder?) But out of work. In pencil is written "disabled soldier". Number of children under 18 for them is listed as nil. But that would tie in with your Mary J Williams being born in 1923. The census also shows a Daniel Morrissey (brother in law) aged 51 born in Templemore, so maybe Marys brother/ maiden name? Good luck with your search