Thank you all for your responses, it is all food for thought, and introduces other avenues to explore.
The Edward Blanchard who died at sea in 1868 (NSW) was only 22 years old, so not the right guy sadly, but there is no evidence to suggest that Edward came back to England with Maria and Algernon, as Maria was the informant on Edith's birth certificate. Maria remarried in 1884, and gave her status then as widow, so she must have either known or assumed that Edward was dead by then.
Algernon did travel back to Australia, where he settled and raised quite a large family.
I do feel that if Maria had given birth to Edith, then she would not have put her on the census as an orphan. Maybe Edith's birth mother did travel back from either Australia or India with Maria, and died giving birth to Little Edith, who Maria then adopted. To me this seems the most likely scenario, but I've a feeling that we shall never know the truth.
Thank you all again for your input,
Carol
