Not easy to achieve, and more expensive items aren't necessarily better in terms of workers' wages and working conditions (there were high-end brands in the wreckage of Rana Plaza along with cheap fast fashion) or the environment, as well as other concerns.
Upcycling of clothing is becoming more and more popular in France, at least among younger people. The older generations don't really understand since most of them (us) tend to wear clothes a lot longer and they are mostly worn out when disposed of -- so they go in the clothing bins but mostly to be transformed into paper or things like that. The younger generations are beginning to understand that they buy far too much and don't keep it very long, so resale has become a huge industry. The Lithuanian site Vinted seems to be the market leader in a lot of Europe. I don't know if their business plan is "ethical" but at least they give the opportunity for millions of people to buy used clothing at a reasonable price.
But even the major companies like H&M or the Auchan hypermarkets now take back used clothing for a credit. And then there are the shops which used to call themselves 'vintage' shops but which now recycle everyday items. Kilo Shop in France sells clothing by weight (I don't see them selling very many winter coats.) and I cannot pass the used clothing store Guerrisol without spending 5 minutes pawing through the crap. The shirts all cost 2 euros, for example, and I picked up a Ralph Lauren polo shirt in pristine condition once, although most of my finds are a lot more ordinary.
I read that Guardian article too. It is a dilemma between buying fast fashion (I used to stop in to Zara whenever I was in downtown Toulouse) and really high end brands. I refuse to spend those amounts of money on clothes -- like over 200€ for a blouse, but don't buy the crap at Primark or shops like that.
For the time being, my dilemma has mostly been solved because I haven't bought anything for ages, except 2 t-shirts on sale last year. And a Ralph Lauren dress for 2 Euros in a charity shop. I haven't worn it in fact, and only bought it because it cost only 2€.
More seriously, I believe it is rather hypocritical to worry about low wages in the third world clothing industry when minimum wages in our developed countries do not allow people to buy new clothing except at rock bottom prices (and yes, I shop at Primark sometimes because I have found that many of their tshirts for one euro are of very good quality -- should I boycott them? Then again, I don't buy any very often because they last so long.). Minimum wages in the rich countries would have to be increased considerably to allow people to buy 'ethical' apparel. And that is even without worrying about the Bangladeshi or Pakistani workers losing their jobs because we want to pay more.
I lost a considerable amount of (menopaausal) weight when I was hospitalised, so do need a few more jeans and other items that aren't worth "retouches" (alterations). I will be buying those new as although I'm markedly healthier and fitter, I don't feel quite ready to go shopping (whether "preloved" (gag) or new. I'm buying exactly the same black jeans I have on. At least the almost new too-large ones given to a charity shop will make somebody happy.
I've seen that certain fashionistas even have clothing racks in a converted garage. I'll never be that person, not even if I should come into an inheritance.
I will try to buy a new-to-me winter coat at a charity shop, though. I've had luck with those.