I bloody love Cos and a good chunk of my wardrobe is from there. I've always done big sales orders online but like Judy was caught out last time by the change to Hermes (DPD shop is round the corner), there's a Hermes near my work but carrying one of their huge boxes on my morning commute is Not Fun. They used to let you return by post, I suppose at least store returns would make things a bit easier if you happen to be near a shop...
Anyway returns gripes aside, I love their trousers, knitwear, t-shirts, shirts, jumpsuits (really love the jumpsuits), coats, blazers, accessories. Dresses are a bit more hit and miss for me but I still have about half a dozen!
As PP said, they don't date as much as some other brands; I'm still wearing Cos items I've had for nigh on a decade (particularly a couple of thin stripy tops with a neckline more scooped than they'd sell now, but which layer beautifully under the aforementioned jumpsuits).
FWIW I'm 5' 9", pear/hourglass, size 14, take a Cos 40/M.