Milk is delivered to the School of Computer Science every morning, and put in the basement, next to the doors in the South-East corner of the building (i.e. next to the undergraduate common room).
If there aren't many milk bottles in the fridge early in the morning, probably no-one has collected the milk yet, so please do this yourself! No-one seems to have explicit responsibility for this, but if it doesn't get done the milk just sits in the basement slowly going off.
A higher proportion of milk should go to the first floor kitchen than the second (this is because both the ground and first floors use that kitchen). Empty milk bottles should be rinsed out and put in the crates; crates containing empty bottles should be left by the doors in the basement.