Some info from electoral rolls - two men with similar names:
1916, 1917 at Wood St Osborne, WA
George Spencer WALLIS, attendant, Mary Elizabeth WALLIS, hd
1922
Spencer George WALLIS, fireman and Mary WALLIS, hd at 40 Wood St, Fremantle (It may now be the suburb White Gum Valley)
1922 George Spencer WALLIS, fireman listed at 58 Railway ST, Cottesloe - no-one else of that surname listed at this address
Unfortunately I don't have access to South Australia rolls.
There are a number of men listed in Victoria and WA with the second forename Spencer. The next entry I can see which uses Spencer as a first name -
1937 at Applecross
Spencer WALLIS
1943 at Fraser St, Applecross
Spencer WALLIS, gardener.
I see Mary WALLIS, pensioner, in Coolgardie in 1949, 1954 There are other listings in WA but it's not an uncommon name so I won't put them up.
Judith