Sansucre correct me if I'm wrong, but Samantha Cameron is merely a brand ambassador for the BFC - it's a classic corporate wife role which she got because she already has a public profile thanks to her husband.
She gives drinks parties at 10 Downing Street for fashion designers and brand managers, goes to fashion shows, and wears British brands when appearing in public. That's about it. Sarah Brown used to do the same - another English premier's spouse who has absolutely zero credibility on the style front.
Both SamCam need to dress professionally and anonymously if they want their charity and public relations 'work' and not their clothes to be taken seriously.
Both SamCam and Kate Middleton need less fuss, and more tailoring. I don't think it's an accident that SamCam looks her best when she's going to work (in her real job at Smythson).
KM needs to wear longer skirts for practical reasons, even if it involves some SamCam-style fakery in the style of the M&S dress. She also needs to dress appropriately for her age - she seems to think this means shorter hemlines; it doesn't. The best I've ever seen her is when she was wearing navy Smythe jacket and dress. She looked businesslike, intelligent and confident rather than girly and frou-frou.
They both need to stop doing piddly little 'in the know fashionista' designers and start dressing in big British brands that have expanded rapidly in foreign markets: not only Burberry and Mulberry, but serious big business hitters such as Topshop, Marks & Spencer and Debenhams (yes, really).
This is what will bring in serious foreign revenue into this country; some £4000 dress from a designer who sells a 100 dresses a year is pissing in the economic wind.