William,
I suspect the reason you can't find it on Genuki is because the ecclesiastical parish is, or rather was, Balby with Hexthorpe. Having said that, Genuki doesn't seem to have a separate entry for the parish of Balby either!
This is what the gazetteer says for Balby with Hexthorpe:
Former urban district and parish, West Riding of Yorkshire, on the river Don, since 1914 included in Doncaster; ecclesiastical district St. John the Evangelist, population 8,539 (1951 census), Post Office.
Called Balby.
Jon