Yes, this is more than likely his first wife but I have nothing to back it up with. However, I have since found a Susanna Bisby born in 1841 so I have ordered her birth certificate which will give me the names of her parents.
It does seem odd though that although they married in 1826 (assuming it is the correct marriage) I can only find details of the one child born 15 years later - seems a long wait.
Thanks you both for your invaluable help.....greatly appreciated.