What is the distance between London and Melbourne Australia?

"some where between 18 and 20 hours"

I believe the question asked driving times. Anyone can fly to Melbourne.

The most direct and adventurous way to drive would be through Europe, Turkey, Middle East, India, Thailand, Malaysia.

Then will begin the first of a few aquatic legs of the journey via Indonesia to mainland Australia. The closest mainland is in Western Australia. Best to find a road or there will be some unpleasant desert driving. From Broome t Melbourne is a comfortable 5000km.

Enjoy your drive