I'm 48 and find it easier to buy clothes now than in my early 30s. Then I looked very young and wanted to look older to be taken seriously at work and that balance between how I wanted to look and what was actually available in my local shops was hard. It's why Boden became so big, they had a good website very early on.
As you get into your 40s I think you can get away with dressing 'younger' and still look serious so women in their 40s and above have more confidence buying from a wider variety of shops.
Here are the places I've bought clothes and shoes from in the last year: Arket, Disko Kids, French Connection, Hush, Toast, Boden, Sockshop, Rogue Matilda, UNIQLO, Top Shop, Dune, Zara, Schuh, Mint Velvet, Next, Other Stories, COS, ASOS, Gap, Jigsaw.