For me, non-frumpiness is nothing to do with brand or style, it's about attitude. There are older women in my writing group who rock all the "wrong" things... tunics, scarves, colour, dresses with trainers, coloured footwear... Fatface, Seasalt and whoever else we're supposed to turn our noses up at. These women are all shapes and sizes and they look fab, because they're animated and honest and comfortable in their skin.
What looks frumpy to me is someone trying to keep up with 30- and 40somethings, and failing because a lot of fashion is uncompromising and uncomfortable, and deliberately so, because it's how younger generations distinguish themselves from older ones.
For example, I've always loved jersey widelegs (they're not a new invention!) but my changing body shape - by which I mean drooping! - means I can only wear them with tops that cover, or at least don't emphasize, crotch, tum and bum. Moreover, the 'neat fitted top' you're supposed to wear with widelegs is generally not a great look on post-meno boobs.
I've just been listening to an interview on Woman's Hour about 'women designing for women', as women have become Design Directors at Whistles, Uniqlo and M&S. There was predictable stuff about how they understand what women want, and isn't it great that before, women were condemned to frumpy clothes when 'they' (curiously the interviewees never referred to 'we') got older, whereas now they can wear the same clothes as their teenage daughters.
To which I thought, no, not buying it. There are a hundred reasons why I don't want to wear clothes designed for much younger women. I'm sure that somewhere out there is a brand that's designed to flatter older bodies, and doesn't cost a fortune like Hobbs, Whistles etc. (The idea that older women have wads of cash to spend on clothes is convenient for retailers and their promoters, but hardly reflects the 'real lives of women' they claim to know so well.)
Anyway, if anyone's found such a unicorn please let me know! Meanwhile I'll bash on with making what I think/hope are judicious choices from the likes of Seasalt, M&S and H&M, treading that fine line between fashion, comfort and not scaring the horses.