You can find out direct on the Virgin web-site.

If you try to book a flight between LHR and Sydney, it gives you an option to choose a stopver both inbound and outbound.

An economy return with stop-overs both ways will cost £678.70,
An economy return with one stop-over will cost £643.80
An economy return with no stop-over will cost £608.90

The level Virgin tier points you also vary; more with a stop-over.