I hate

We share milk, well, I share milk it seems. I buy 2ltr at a time, my flatmates both get 1pint max at most every other time.

I Often get milk which I never see, or worse, I find it opened, 4/5 full, left out the fridge all day.

Now and again I've taken to pouring full fat cream into their skimmed pints to sabotage their diet regimes.

Simple solution - go vegan and use soya milk. It takes a wee while until you get used to it (and you do) but you can guarantee that no one will nick it because to tthe casual user it tastes vile in tea.