I used to get quite a few things from M&S. Now it is bras, boots and jeans only (plus if I pop in for food). Their suiting used to be excellent - you could get some quite nicely tailored separates which were quite hard wearing and washable - but I am unimpressed now.
You could try online stores such as Roman (I've bought some nice clothing from there which lasts including some nicely tailored stuff, but also some more casual stuff); Klass - but I've gone off them, they are all a bit cardigany now whereas 20 years ago they were better.
I have found that shopping in smaller niche stores online you can find some nice stuff - but I understand you do not want to shop online. (I prefer it, because I hate changing rooms).
Have you thought about going to a designer outlet near you? There are loads of those round the country now - they are not really designer - they are really end of line stuff sold in stores, but even so, you can get some good quality stuff.
I used to love M&S, but they just dont do it for me now.