And .. (sorry for lots of questions!)  -  1911 has the 13 yr old Martha Isabella junior.  But the 1901 doesn't have her as a 3 yr old - instead it has an L Jane aged 3?  Have you found out where Martha junior was? I assume the children from 1901 all died before 1911.  
Not that any of this helps find William's death, but just trying to get a full view of the family.