I find in Tesco and the Coop (don't think I've used M&S) they let you say you're using your own bags, but they assume that's a carrier bag and complain at my ru

I find in Tesco and the Coop (don't think I've used M&S) they let you say you're using your own bags, but they assume that's a carrier bag and complain at my rucksack. I always leave packing until the end if I can now, although they'll still complain about unexpected items even after paying..