I'd neglected to check how charged my camera phone was though - so I turned up with 17% charge left and, after climbing through the fence into the building site (as is my wont), I snapped like crazy until the phone karked it a few minutes later.
The signs were from before the 1950s it seems - this is backed up by the 1950s two-tone brick style of building that had been demolished:
The revealed signs are fabulous, with more exposed with the progression of the demolition works. One wall appeared to be a wall advertising a range of products to passing traffic, and the other side was an automotive centre specialising in tyres. The signs are layered. One side has a sign for butter menthol drops beneath a Persil washing powder ad (for Persil's history, see: http://www.henkel.com/henkel-headlines/2006-18539-100-years-of-persil-11029.htm). The drops sign has the signwriter's signature: Edgar Hook Signs.
Here's what the Persil sign once looked like, thanks to the Stonnington Council website (http://stonlib.stonnington.vic.gov.au/cgi-bin/spydus.exe/ENQ/PIC/BIBENQ?IRN=6401817&FMT=PA. What's interesting here is that a) the signs below the Persil one are older than the photo (which looks like the 1940s), since they predated the construction of the bakery building, b) The Persil sign was painted quite sloppily on top of the butter menthol sign, which looks like it was for the Allens brand (look above the 'Persil'):
Underneath the Persil sign (see below) are older signs for Pennants next to the remains of a painting of a cricket player. Palmer's Pennants was something sports-y (bats? balls? muscle rub?) but as yet my Google searching has turned up nothing...any help much appreciated.
On the wall opposite are lots of layered sign for Dunlop and other tyres, as well as what looks like older signs for a Ford dealership. I'm including all the photos below. Who knows how much longer these signs will be around? John Hunter's website also has some more photos of the site: http://jalbum.net/browse/user/album/1482256.
Anyway, here are the pics: