> Ocado can only work with packed goods - not weighed vegetables for example
Not quite. Packed yes, but for many vegetables they have both item count and weight-based packages, e.g. "4 potatoes" vs "1kg potatoes".
I think that strikes the right balance.
Interesting, however in my case we have someone who eats a banana each day with breakfast. There's no way to buy 7 bananas in your weekly shop!