Looks like an acacia (wattle) of some kind.
According to my Australian Natives book, it could be Acacia pycnantha - Australia's floral emblem. Grows to 10m tall, grows fast in well drained soil. The seeds are edible. The flowers are very pretty.
Thank you so much @bluebec!
10 metres! It looks like a lovely tree but it's totally in the wrong spot. I will ask them to move it. Wish me luck!