What flower is this?

I have a flower book that often helps me out when I have a query but this time I'm absolutely stumped.  I have been passing this flowering shrub every time I drive into Blackheath.  This afternoon I went in search of it again and brought a couple of sprigs home with me to photograph with my macro lens.  The little bell like flower is absolutely tiny.  I was thrilled when I saw this on the big screen.  The flower looks almost transparent.  I would love to know what it is.  I'm sure there's a very knowledgeable blipper out there who knows the answer.