I think I have this look. Quite interested to see it's so coveted though as I was out shopping yesterday and was thinking how I always feel so underdressed compared to so many people in the city. For me there's no secret to it though, just laziness! While I love clothes I'm not that fashionable and I'm pretty low maintenance. People say I always look well put together though so I'll, ahem, give you some tips in the hope it may help:
Hair: my hair is pretty shit and thin but I do grow it long, get it highlighted every couple of months and wear it in a loose bun/ shabby high pony tail falling out of a bun whenever it's having a bad day (most if the time)
Skin and make up: I have good lightly tanned clear skin which is just luck and good genes, just as well as I hate make up. I wear Liz Earle / Laura Mercier tinted moisturiser along with a few sweeps of light bronzer and cheek highlighter (body shop). Mascara, eyebrow pencil but not too much. Eyebrows I keep shaped but not overly 'done'. Evenings I'll wear some neutral / smokily / gold eye shadow (urban decay Naked Palette)
Jewellery: for daytime, always pearl studs. Silver chunky ring, platinum wedding band. Big leather or small stainless steel watch. No bling. For evening I might wear big costume jewellery - chunky fake jewel rings / tarnished charm bracelet / bangles / tarnished earrings or big hoops.
Accessories: lots of scarves! I have a whole section of wardrobe dedicated to them!
Shoes: pumps, converse, cowboy boots, riding boots (mid calf), biker boots, metallic sandals. High heels for occasional evening and work only, never over four inches!
Clothes: skinny jeans, usually from 7 mankind or H&M, layered vests and t shirts, collared shirts with v necks, blazer jackets, leather jacket (scruffy). Summer dresses. Lots of stripes and boat necks.
Bags: I have a nice collection of Mulberry bags, a couple are big shoulder ones but I prefer my more practical cross-body satchel and messenger style ones.
I don't shop anywhere special: Zara, Toast, All Saints, H&M, Uniqlo, French Connection and Great Plains. Superdry do nice boots.
Basically it's the opposite of Victoria Beckham's look. If it feels like too much effort or too uncomfortable I won't do it. Just remember to have nice skin, highlighted hair, minimal make up, skinny jeans, flat shoes, a scarf and a pair of pearl studs and you'll probably pass!!
Sorry about the essay. Me me me... 