For Walter:
There are two possibilities b. Hartlepool (not Scotland, but they both seem to have Scottish)
Walter Frederic(k) Campbell Ramsay b. 1874 married 1894 to Rosa Kate Smith in London, and from online trees it seems that she remarried in 1902 (in Hampshire, to Alfred Edward Elborn). He was born Durham (but may have had Scottish connections). I believe this is likely to be your man - possibly he scarpered with Elizabeth?
I can see his two daughters with Rosa Kate (Elizabeth Maude Mary b. 1894 and Kathleen Winifred as "Winifred C") as "Ramsey" in the 1901 census in Brown Candover with their Smith grandparents.
There was also a Walter Frederick Campbell Ramsay b. 1879 (birth reg early 1800) also in Hartlepool, son of Daniel and Eliza, and this one did move to Australia (unclear precisely when) and died in NSW 1967. He, along with what looks like his entire family, moved to NSW on the Cuzco in 1888 - so he is not your man but his presence in Australia may cause some red herrings.
The 1874 Walter:
Born the son of John and Elizabeth Worthy (nee Thompson):
https://familysearch.org/ark:/61903/1:1:NX67-4DZ (his birth)
https://familysearch.org/ark:/61903/1:1:NNNF-K37 (the marriage)
His mother remarried by 1881
https://familysearch.org/ark:/61903/1:1:X3RD-Z7CDeath for John Ramsay, 1875, aged 28 and remarriage for Elizabeth Worthy Ramsey to John Hunter in 1877
Not born in Scotland but definite Scottish connections in the family - his stepfather at minimum.
If Walter and Elizabeth went to Australia, they must have done so under new names. I also don't see any likely remarriages for Elizabeth under Davenport or Ramsay in England.

Scrolling through a list of Elizabeth Jane deaths in Queensland now - none linked to Davenport or Ramsey but how about:
Jane Elizabeth Robertson, d. 1943, parents not listed but born
Hampshire aged 81.