Hi Jane,
I can completely understand where you're coming from. I live in what was once a thriving market town, until Tescos opened here that is. The market has gone and the town centre shops consist of fast food takeaways, pawn and charity shops, that's it.
I have a car so I can get to local farmers market, which is brilliant, for fresh vegetables etc. But when I want to buy some other products I'm forced to use the supermarket. I have discovered that there's a food coop about three miles away, though. So I'm going to check them out soon.
You may find this list of interest; it details all the food coops in the UK.
http://www.sustainweb.org/foodcoops/add/Thanks for stopping by and reading, Jane.