Perhaps the batteries aren't as good as you think or the last charge
was longer ago than you remember.

4 sets of batteries were all good order and fully charged the day before
leaving and were all flat or almost flat on arrival.

I cant think of any reason why either. Its an odd one )

And it wasn't a one off, I've done this journey a few times, and had the
same results. Its a long trip, UK to Australia, 3 flights, 22 hours in the
air. But radio, camera and phone were not switch on during this time.

Suggestions welcome................