Well cut, beautiful basics. Would happily pay more for a well cut shift dress, fitted jacket, good jeans, a tight good quality t shirt, a white shirt. Things that make a woman look and feel good. This could include angora/cashmere cardigans, jumpers. But please make them suitable for women other than grandmothers and we might actually buy them. The older you get, the less likely you are to get away with cheap clothes. It's about the cut and the quality of the fabric. Doesn't have to be bang on trend. Like what M&S used to do, like.
Decent bloody nightwear. Not crappy PJs with teddies, lovehearts, stupid logos or other crap on then. Plain, comfortable cotton, up to being put in the wash every morning and not falling apart in 3 months.
Decent underwear. Again, less on the sexy and more on the looking good on the female form. Most of us don't give a shit about looking sexy but we like to look stylish and slim, even when we aren't necesarily.
Look at the classics that Kate M and now Meghan M wear. Classic cuts, good quality.
The 'Look expensive' threads on the Style and Beauty board should be what M&S aspire to. To be the 'Go-To' place for a woman to go to 'look expensive' with yes, often plain, classic basics that can be dressed up according to the woman's taste and to the occasion, without feeling that they are wearing the same bloody outfit as the next woman. A well cut dress is a thing of beauty, and can be changed with deifferent shoes, scarves etc. M&S doesn't have to provide all the different shoes or scarves, in fact it's better if they don't, but if they provide beautiful basics, women will buy them.
I really hope they do