Hello Blacksmithy
You may already have this info ??
I had a look at Christchurch Electoral rolls >
Christchurch East Roll   1905-06 and 1908 - William and Rhoda WELSH - at 
100 Hawdon Street, Sydenham   
1911 and 1914 - Christchurch East roll -  both are now listed as residing at 
No. 12 Hawdon Street, Sydenham-  William's death notice of 1916 (died at ChCh Hospital) but mentions  
12 Hawdon Street.
William apparently died Intestate and it wasn't until 
1963 that a claim was officially made on his estate.
The following article shows the "for sale" notice for 
12 Hawdon Street ... 
"Sydenham Cottage on a small section ... Beautifully clean and tidy .... 
situated just by Brougham Street " :
.... On account of the Administrators in the Estate of the late William WELSH :
https://paperspast.natlib.govt.nz/newspapers/CHP19630622.2.214.7    ~   Lu
Edited to add:   Hi Blacksmithy ... I realise in having re-read your query, that it was more info you were wanting for 
100 Hawdon Street.  However will leave my replies in place here in case they are of use.     
