Hi Sue,
I see there was William Selby BLAIR buried at Cheltenham Old Cemetery aged 74, unfortunately I do not see a date.

He appears on the Electoral Roll for Queensland in 1913 and then in Vic by 1936 Sandringham. I do note the birth of a William Selby BLAIR in Ipswich in Suffolk Sep 1889 4a 792.
If it is same person he would have died about 1963 which does not quite fit with the family lore
There is an immigration record for
BLAIR Mr W S departing London 30 Sep 1908 aboard the
MARATHON ticketed to Melbourne. He was aged 19 (a clerk) Country of last permanent residence England - intended permanent residence in Australia.
Traveling with
BLAIR Mr M 44 Typist
BLAIR Miss M C 16
BLAIR Miss J H 11
The occupations seem wrong (I note William Selby BLAIR is an Engineer on the electoral roll entries) but William Selby BLAIR from Ipswich was the son of Mathew S BLAIR (an electrical engineer) and Amelia J. 1901 sisters Mary C 8 and Jessie H 4 so I think it is the same family

Hopefully someone will help further with the death.
Cheers Kris

PS Good one Mandy - fits with what I have found.