I believe that the Henry Diplock in the 1901 census was the son of Walter Diplock, both of whom were born at Bullock Down Farm in Eastbourne. Along with my great grandmother Minnie Diplock who I think was Walter's sister. When I get her birth certificate I will know for definite as Mary Diplock would have been 48 when Minnie was born! and Walter would have been 25!
Unfortunately I don't know much about Henry's family after the 1901 census.