I think BHS went under because it was catering for a demographic which doesn't exist any more. People do not morph into a sartorial middle age any more. No more, on the chime of the clock at age forty, do we have to abandon our jeans for the twinset and beige cardigan.
It is perhaps a good idea when older to choose clothes which are cut well, are lined and are made of decent quality fabric as we cannot distract attention from a charming dishabille by the glow of our skin and the swing of our hair. A more groomed look is, possibly, the way to go.
I concentrate on a facial regime of fancy creams (which don't work, obviously), and exercise and diet to keep trim. At seven stone I can still wear skinny jeans but twin them with 'posh' tops from Phase Eight, Hobbs or like high street top end shop sales. I can't afford to pay for the quality I aspire to so I never buy at the given price but always wait for a knock-down or two (or three).
I find that a very good coat will give a satisfactory 'outline' and, again, I buy bargains. Buying a coat in summer is a good wheeze if you can locate one.
Black lycra tights are the older woman's friend. In fact, they are every woman's friend.
The last piece of advice I would offer is not to give in to old lady shoes. You don't need to wear stilettos but proper, leather shoes are essential for not 'go[ing] gentle into that good night'.