The actual amount at the end of the equation changes throughout the course of a day. One really easy way you can find out in the future is to go to Google, then type in something like 48 pounds to Australian dollars and it will give you the current exchange rate.
At the moment, @meiosis is correct, it exchanges to roughly 75 AUD.
You can get up to the minute answers to this question at www.xe.com
This is the site I use most frequently when I want to know an exchange rate. The exchange rate shown here may differ from the rate charged by your bank when you make a purchase though, so be wary of this as banks will always make a little money out of you when they do this kind of thing.