Hi, My ancestor was also William Millard born Horningsham in 1815. I did quite a bit of research 2001-2003 and obtained a lot of information. I then got side tracked by my mother's side of the family and then let it all go. I have now decided to have another go with so much available online these days. Did you get past William after?
All the best,
Gareth Millard - son of Les, son of Thomas, son of Charles, son of Alfred who was William and Elizabeth's son if my memory is correct.