Ambers, got me thinking.
There are directories in Cardiff main Library in central Cardiff dating back many years. I know they list by street but I can't remember if they list by name too? Its up on the 5th floor, all sorts of local info there.
Does your ancestor have a unusual name? I could have a scan when I'm in there next for the 1925 edition if they have one. Though if its Davies or something I haven't much chance of spotting the right one.
I found it interesting to read who lived in the house I grew up in before my family did.