Exactly right rosie99. That was what had me wondering if I had mixed up 2 families, but from the census entries it doesn't look like it. Another of those mysteries we might never solve I guess. Although, there seems to be a habit of using different names with this family: son Henry (Baptism cert.) known as Harry (Marriage cert.) and Robert George's younger brother was baptised Frederick Thomas but known as Thomas. All adding to the confusion!
Thanks again for your help.