Not quite. Ocado[1] (who I use almost exclusively), lets you fill the basket full of food, and then when you pick a slot, it tells you what's out of stock for t

Not quite. Ocado[1] (who I use almost exclusively), lets you fill the basket full of food, and then when you pick a slot, it tells you what's out of stock for that delivery slot, letting you pick alternates if available. However, the 'correct' way is to pick the slot first, as that way you can see what's out of stock as you shop - this does put you on a time limit though, as the slot can only be held for 1 hour (I think). So it's not enforced, but it is preferable. --- [1] pre-corvid-crisis