On the take back front, some things are happening (I have no idea what though - this should help: http://www.defra.gov.uk/environment/waste/topics/producer-responsibility.htm). This seems to be more about producers, rather than small suppliers, taking back their products. I think a lot of bags are becoming biodegradable, which helps, but a bag tax is a long way off. I guess the easiest thing to do would be to use your own bags for your shopping, thus removing the problem.