It's a bit of a conundrum, what family history isn't.
I found the Lancing entry later and then found 14 year old Cornelius as GLEW in a Chichester residential school in 1871. PRO RG 10, folio 27, p. 13; Chichester He was getting an education, but was he a willing pupil, or was that an institution? Either way, he may have obtained basic skills in literacy and numeracy which may change the way you think about him.
As for Harriett, after the loss of her mother, she is unlikely to have traveled as an infant just with her father, so I would consider looking for her with her grandparents or the family of one of her father or mother's siblings. A possibility is that she may was then known by their surname rather than her own. Her true surname may only have been revealed when the workhouse in Petersfield sought a contribution for her upkeep from the parish of her birth. Harting still seems to be a strong contender, so it may be in your interest to look at the records of that parish a little more closely.
Rootschat prefer us not to put in links to other websites, so Google " Glew Jon's home page "
and you will find a guy to contact who already has an interest in the Glue/Glew family from that location.
Regards Roy G