They all seem very inconsistent to me, and also some seem very overpriced and trading on their name of having previously been much better. (Jigsaw, Whistles, Hobbs) I'm looking at you.) Dresses getting into the £150+ range with dodgy seams, wrinkly materials and inconsistent sizing even within the same dress!
I think shopping around and actually feeling the different fabrics is key. Uniqlo had some lovely basic pieces in - their satin skirts even come with an under slip - and some of their t-shirts are a decent cotton. Trousers more variable but some of their heavier pleated front ones sit really well. But their cashmere and merino knitwear seems to shrink or bobble or just wear quickly in my experience.
&OtherStories is quite expensive but at least interesting in terms of fashion/shapes. Again I think overpriced initially but not too bad in the sales. They also do nice accessories - especially their earrings.
Cos/Arket have good basics - but sometimes H&M and Monki have similar stuff at lower prices.
Going to John Lewis and browsing the different concessions will give you a wider choice and a better feeling for what's available. The John Lewis anyday range sometimes has some really good stuff at a reasonable price.
Anthropologie has interesting stuff at different price points and again good sales bargains to be had.
But generally I think previously higher end high street brands have become vastly overpriced with the quality the same as the more budget brands - so better off spending time in places like Uniqlo, Zara etc and rooting out the things there that look more high end but with a more wallet friendly budget.
And even the supermarkets have 'copies' of some of the higher end brands and the over quality isn't really that different! I have had some great stuff from the TU range at Sainsbury's - that have far outlasted and been worn more than some of my more expensive purchases from other high street places. Like their jeans or quite well cut shirts or summer dresses.
I think what I'm saying is shop around with a wish list - and be open to taking some time to find the gems that work best for you