I started getting my shopping from Ocado when we were in lockdown, and I've never had any items missing from my order, or substituted. Their system is efficient at marking goods as sold out, or unavailable for your delivery, BEFORE you check out, so avoids you relying on the delivery and then getting disappointed/surprised. Only one negative experience when a delivery was super-late, due to severe traffic delays. The delivery people are courteous and efficient. I have tried four other major supermarket suppliers, but none are as consistently satisfactory.