The more time I spend on the womenswear section the more problems I see - and that's just in one mornings' procrastination at work! 
The whole Limited Edition section should be binned (70 items). There's not a "staple" there - everything has embellishments or some fashionista thing going on. It's like looking at Zara or Mango. Bin.
Autograph seems mostly ok when it's black/white/navy, but the prints are awful and colours sludgy or a one-off - eg. gorgeous canary yellow jacket, why not in a cool colour as well? Again - 185 items to wade through. Bin all prints and most colours.
Classic, 128 items. Prints again are almost universally terrible and almost EVERYTHING is printed. Or some kind of weird pebble-dash like the designers can't bear solids. Just - why?? Bin anything that's not a solid and see what's left.
Twiggy. Why have a separate range of yet more items, many of which make Twiggy herself look dumpy. Why not an edit from the main collection of some kind. Bin.
Per Una. There must be a market for this stuff or they wouldn't keep making it so I guess look hard at the range and edit it down. Not even the most dedicated Per Una fan could wade through 238 items. Remove everything that's embellished and then streamline the rest of the collection. A lot surely overlaps with the main M&S Collection eg. the many many different kinds of jeans, chinos, cotton trousers. Why repeat them in Per Una?
M&S Collection. 1698 items. Oof. But, ok, this is the core of the whole shop. Eliminate anything with embellishment, slogans, and most of the prints. And then edit, edit, edit.
Interestingly if I go to the Boden website and say "view all" for women there is a total of 405 items TOTAL. Of course many of these will have 3-6 alternative colours and patterns but still, it's not so overwhelming to look through.