I think some of the problem is that M&S haven't made that mental leap from being a food shop with physical customers to being an online store.
They haven't understood how differently the two types of customers shop, and what their different expectations are. This would explain why some of their packaging is very flimsy, and why their stock levels/availability have baffled so many of us, and why they seem to suddenly have availability of some fresh items now - when it's too late for online shoppers.
I know I would have bought more items, if only they had been in stock! My order is due on 22nd, so I'm awaiting it with trepidation!