It depends. Personally, I prefer to leave in the evening so that I can sleep on the long leg from London to Asia. However, you arrive in the early morning in Australia which means a long slog to stay up and try and beat the jet lag.
Some people prefer a PM arrival so that they can go straight to bed.

One way I've done it before is to take a couple night stop over in Singapore. Leaving London in the evening, arriving SIN in the evening, straight to bed. This has helped stagger the jet lag.