Thank you all so much for your help - it was wonderful to read the replies as they made lots of my other information suddenly fall into place! I am now starting to understand where I fit in. Being new to this and finding myself swamped with Oriels I had naively trusted an Oriel family tree structure that I found online and tried to use it to match my own information - I have now confirmed that there were errors in it which caused me to go wrong and I have learnt my lesson!
Could I please follow up? I now believe that this is indeed the correct John Oriel as it matches direct evidence from my own family and I am now wondering about two other children.
It seems that his first wife, Margaret Harts, may have had a daughter, also Margaret, when she was only about 16, but I can't see what happened to the child after age 10. Does anyone know? She seemed to be called Margaret Oriel even thought her mother didn't marry John until much later, in1872.
I think that there was also a Mary Louisa Oriel (known in our family as "Aunt Louisa"), daughter to John and his second wife Annie. I know she was a teacher but I am keen to know more about her if anyone can help.
Once again, thank you for the help and advice - and I will look into all your suggestions.