Just read this expression on another thread- Genius! As in, teenage dd has failed to get all her shit in one sock - (disorganised)
Other current favourites-
Put your pom-poms down (used when people get a bit ranty and over passionate about stuff, stolen from Gwen stefani)
And ‘she looks like the cat’s just crapped in her handbag’ - when people get that sour faced, pissed off look. Also from mumsnet.
So go on, what are your classic expressions? I need a few more for my repertoire!