A different option would be to get a Google Voice or Skype number in the UK. This way you can make and receive calls and texts over the Internet as if you were in UK.
I honestly don't understand at all why you would need approval from a government agency whatsoever.
Just get a friend to buy a prepaid simcard for you in Australia, have him validate/activate the card in Oz (important), then send it to you by courier. It'll work just fine here when you set it to "roaming".
Don't ask anyone's permission.