Hi Jo,
I have had a reply from Mike regards your question.
His gg grandmother Mary was William's sister, so although he has William in his tree, he also has no information on marriage details to Mary.
He seems to think 1836 marriage date could be wrong as there is no such date recorded in Luffenham Parish records. Did you get 1836 from LDS? They are not accurate from my experience.
William was living with his parents and brother in 1841 census.
Harriet I believe was William and Mary's first child she was not born until 1845 and according to Mike there are no suitable entries before that date.
I will send you a PM with my e-mail and will also pm Mike.
Best wishes Kim
