I think M&S is trying too hard to have something for everyone. I used to be able to guarantee i could find something in there. As a size 20/22 I do struggle to find nice, fashionable and quality items. I used to find something at M&S. Not now.
The larger sizes collection they did was dreadful - aimed solely at the over 60s. Now they say that a lot of their items are sized up to a 24 - no they are not!
Kids' school uniforms - great.
PJs - kids and adults - also good.
Underwear - bras - fitting is rubbish if you don't fit their standard sizes. Their control wear is good.
Shoes - used to be able to find something nice but not recently.