If you need to head out to Australia before the end of March, Etihad Guest is offering a decent double miles deal.
You will receive double Etihad Guest miles when you fly to Sydney, Perth, Melbourne or Brisbane with Etihad or Virgin Australia. You will also receive double Etihad Guest miles for all domestic flights on Virgin Australia.
Etihad has a 10% equity stake in Virgin Australia, although it is not part of the Etihad Airways Partners alliance, which explains the rationale behind this offer.
The window to take advantage of the deal is quite narrow:
you need to book by December 25th (I assume this only applies to Etihad flights as they would not know when you booked any Virgin Australia flights)
you need to fly between January 26th and March 31st
your Etihad Guest account must be registered in the UK, France, Italy or Germany
you need to register in advance at this website
Etihad Guest is a sensible place to park any Virgin Australia miles. Their own frequent flyer scheme, Virgin Velocity, is only open to people who live in the Asia-Pacific region. You can also redeem Etihad Guest miles for cash via PointsPay at the ‘not terrible’ rate of 0.41p per mile.