We have our office groceries delivered by Tesco and do have the order with bags and pay the extra 40p for it. And it is quite odd how they pack; sometimes there will be 1 large item in a bag and 10 small items loose. I take the bags home and use them as bin liners and give some to my brother and he uses them for dog poop collection in the garden (Bella will not poop out on walks - sorry TMI
) Good thing with Tesco bags is that they are made of recycled materials and I'm sure I've read somewhere that they are degradable.
When I do my own shopping I always use my own bags; cannot think the last time I needed to buy a bag in the shops