I tried to buy a black cardigan in M&S recently for a wedding I was going to. I wanted a plain black lightweight cotton summer cardigan with plain buttons, ideally fairly short, even maybe cropped to waist length to go with a 50s style dress. Could I find one? Could I fuck. I could have bought a nasty acrylic cardigan if I'd wanted. I could have bought a cardigan that was way too long to wear with a dress. I could have bought a cardigan with really horrid shiny buttons. I went to H&M and bought a really plain black cotton cardi with plain black buttons. It was a bit longer than I wanted but a lot less money than M&S's offerings and ten times nicer and more useful as it was utterly utterly plain so I can wear it with lots of stuff. Agree that Uniqlo is doing this kind of thing way better (see also pants).
The kids stuff needs sorting out, too. The girls' clothes are horrid. DD is only 11 and wouldn't be seen dead in the stuff in M&S. It's variously too pink, too bright, too shiny, too babyish, too grown up and too cheap-looking. She likes Gap and Zara and I like their children's stuff better too.
Your underwear department, M&S, is awful. The range of bras outside 32-38 band and A to E cup is laughably small. Your bra-fitting is nuts. A 34B is never going to actually be comfortable on my 30F breasts, never mind provide some support. Your cotton pants aren't stretchy enough and who wants to be wearing baggy pants? I can't size down because you don't do a smaller size. The same size in Gap or Uniqlo is fine on me.
Per Una, as everyone has said, is a joke.
Your shoes are too wide. I know there are people who want wide fitting shoes and you seem to have lots of these but what about those who want narrow fitting shoes?
When I was in my mid-twenties, I frequently bought stuff from M&S. I recall fondly a Ghost knock off dress that had magical pulling powers and was really stylish (still have it). I had a wonderful chunky dark blue cotton jumper that I wore until I couldn't darn it any more. I had some gorgeous thick cotton socks that were amazingly warm - I don't buy M&S socks any more as all the multipacks are either too boring or too pink. My basics, black T shirts etc, were 80% M&S. I'm nearly fifty now and find your clothing frumpy, poorly made and unflattering. I have no idea who it would suit!