Just found something interesting, though it may be what prompted Kath's original query. Googling for "ellis dick hudsons bingley 1967" (just the words, no quotes) brought up a result in Google Books - "Somebody's Husband, Somebody's Son: The Story of the Yorkshire Ripper" by Gordon Burn - it's on page 82.
This does seem to suggest that Ellis was killed almost instantly. It also describes him as "old Ellis, one of the greenhouse staff", so I wouldn't want to completely rule out the 79 year old Willie. However, authors can make mistakes, particularly if they are relying on individuals and their memories rather than written/printed records, so it might be worth looking into similar names as well, such as Elliott or Ellison.
One further thought: this book says the death was "a few months before Peter Sutcliffe was sacked from Bingley cemetery in 1967". That might not in itself preclude, for example, John Ellis aged 70 in June qtr 1966 - though Kath, I note your comment about March-November 1967, which appeared while I was looking into this and typing it up.)
Arthur