In the UK, close contacts are not required to self-isolate unless specifically instructed to (
When to self-isolate and what to do - Coronavirus (COVID-19) ).
One thing that needs to be noted is that if you are infected with Covid and recover in that 14-day period, you still may test positive for quite a while (potentially several weeks), due to viral fragments remaining in your body. For the purposes of self-isolation, most local health departments have a process where you can be medically cleared - certifying that you have recovered and aren't infectious - to release you from self-isolation. But for travel purposes will this suffice? I can't see any official info for Australian entry purposes about a medical clearance being valid in place of a negative PCR test.