I found in the 1934 (Moreton, Harrisville) electoral roll on CD the same as Trish found for the 1936 roll.
Lucas, Beryl Llywelyn, writer.
Lucas, Harry Eyre, writer. Both living at Flinders.
I couldn't seem to find them any earlier than this.
However, I did also look for Harry Giles Eyre, in 1930 he is living in Randwick East in Sydney.
Details are 1930 South Sydney, Randwick East
Eyre, Harry Giles, 104 Mount St, artist. and presumably his wife
Eyre, Elaine Violet, secretary.
Next door at 106 Mount Street ("Yeronga")
Eyre, Violet Maud, home duties.
Eyre, Alwynne Eva, home duties.
Could these two ladies be daughters of Harry (Sr) - ie Harry Giles Eyre's sisters maybe?
Then in 1936 district name has changed to Watson, sub-dist Randwick East.
Harry Giles Eyre same address. No wife.
and only Violet Maud Eyre living at 106 Mount St.
A few of these names could also give some clues. Hope this helps.
Anita