You can try looking on the Family Search website for a possible baptism - but unfortunately William Morris is a very common name, and I suspect there will be multiple possibilities without any way of knowing for certain which one is yours. It's just possible he might appear in the parish settlement records of Ashby Magna, but as he appears to be someone who may have travelled around for work, it's unlikely as these records are usually of people who could not support themselves and applied to the parish for relief. You could also try searching to see if he made a will, which might give some clues to his origins, but he may not have made one.
Have you checked the marriage records and banns book to see if there is any hint about his origins? It may just say 'of this parish' but I've had the experience in my family tree where the marriage record said 'of this parish' but the banns book said something different - worth a try!