As everyone else has said, give us good quality basics in good quality materials, well made. Ditch the gaudy prints and nasty fabrics. Get rid of all the various ranges. Organise the shops better, so that things are easier to find.
But, what's all this about the current ranges being for "over 50s"? I'm over 50 and I wouldn't be caught dead in most of their recent stock, especially Per Una. I occasionally find something in the Indigo range, like a layering t-shirt maybe.
Give us some nice classic stuff - I mean classic as in well-fitting black trousers, white cotton shirts, jumpers / cardis in up-to-the minute colours, that will wash well, won't bobble or shrink after one wash. Get the little details right, like the length of the sleeves, the shape of the necklines, the size of the buttons.
Give us comfortable underwear that will act like scaffolding (holding us up or in) and will look good and feel good. No more crazy-coloured bras with skinny straps and too many seams on the cups. Knickers with decent-sized crotches, lately its like they are skimping on the (cheap) fabric.
I recently returned a two-pack of tights as, when I was putting on the first pair, I put a finger through them. I was so cross, I brought them in next day to complain. I wasn't expecting a refund but, fair play to them, I was immediately offered one. There are still great things about M&S, I find their customer service excellent. I would hate them to go under. Is there any hope for them? The autumn stock thats coming in at the moment is pretty dire. Do they even listen to their customers?