Hi there, this is an issue that has come up a lot in discussions for Brisbane hosts.
It's important that you use the self-assessment tool for a home-based business on the BCC website. (Not always easy to find so if you have trouble I'll see if I can send you the link). You can describe the home-based business as a bed and breakfast using this tool. Hopefully by going through that tool you'll see that you don't need approval. Note that in order to qualify as a self-assessed home-based business the maximum stay for guests is two weeks.
I hope that helps, cheers, Jennie