The reason your shopping comes in multiple carrier bags from Ocado is that it is a warehouse and not set out like any supermarket that you or I would go into. Your shopping could come from over 16 different areas of the warehouse and will have been picked by more than 16 people. All Ocado carrier bags are manufactured in this country and are 100% recyclable. You just hand back your bags to the delivery driver and they come back to the warehouse where they are sorted into their colours and sent off to be recycled. Most supermarkets in this country have their bags made abroad, so the shipping to get them here makes them even less green.
I don't know what Sainsbury's excuse for multiple carriers is!
Used to work for Ocado in the warehouse picking people's shopping - left about 4 months ago. And I would use them for my shopping if I could afford them. The conditions for the storage of food and the picking are very good. There is the odd problem with the picking - things like segregation of raw/cooked meats or someone putting a 4 pinter of milk on top of a punnet of raspberries, but Ocado are continuaaly looking for ways to stop these things happening. The wastage from a warehouse like Ocado is only about 4% which is masses lower than any supermarket.