If you're not looking for top quality meat, Tesco does seriously cheap chicken.
If you want something a little better, every Co-Op I've been into has a habit of over-buying plenty of stock lines and end up reducing things to rock bottom prices at about 9PM at night. Where I work during the Summer, I go in and pick up crusty bread rolls for 5p each and a pack of sausages for 50p. If you're willing to eat the sausages out of date like me (nothing wrong with them - "Best Before" date), then that's dinner and breakfast sorted!