Erm, Catholics are Christians. Christian just means "follower of Christ" and members of all denominations associated with Christ and the New Testament are Christians. Catholics are just a particular group of Christians. You will have been raised in a particular denomination of Christianity too, even if it doesn't feature in your church's name.
Christian was very popular when I was growing up (along with my own name, Christine, and Kristy, Christina, Christopher, Kirsten, Kirsty and a host of other Kris/Chris etc names). I doubt most of the people using Christian in the 70s and 80s in Australia were using it to honour their faith; it was most likely just part of the trend.
I wouldn't use it myself but it's a pleasant enough name and no one will blink twice at it.