Fuck's sake, I've just seen for myself what people were talking about on this thread a while ago re offers being changed after you've bought them! It's outrageous! A week or so ago I added Twinings teabags to my delivery for next week as they were half price.
Just went on today to add a few more things and couldn't believe the teabags were just sitting there for full price at £5! Wouldn't buy them at that price.
It's such a stupid bizarre way of doing offers, by the date you add them even though they know full well the offer won't apply on the delivery date. I always book the delivery date first as well before adding anything.
The flip side is I then went and checked to see if a few things were now on offer (Lurpak, Dolmio etc) that hadn't been when I placed the order, and they were. So I added them.
Fairly sure this has been going on for a while as I'm sure I've looked at my receipt after delivery and wondered why I've bought something (which was probably on offer enough to make it worth trying).