@Mattx - you may well be right. AHD, mw.com and Chambers online :
move about, crowd around, throng, swarm, stream, press around
whereas Cambridge online has:http://dictionary.cambridge.org/define.asp?ke...
mill around phrasal verb (UK ALSO mill about)
If a group of people mill around, they move about with no particular purpose or in no fixed direction, sometimes while waiting for someone:
In the village square, people were milling about in the sunshine.
I've never encountered the Cambridge meaning, and it appears to be in a minority of the serious online dictionaries.
Anybody out there can quote the OED on this?