The item Jenny Tools lists in her answer isn't what I'd call an air conditioner, though I've heard they can be quite effective - it's really just a fan that produces air that has been cooled by being blown over ice cubes. I recently bought a air con from Homebase for just under �200 (they start from �150) and it's brilliant. I live in a 2 bed flat and if I leave all the doors open it cools most of the rooms. It is a little noisy to have in the bedroom (for me anyway, I'm a light sleeper), but you could put it in a hallway say and still feel the benefit. However, they do have an outlet pipe (they extract a lot of moisture from the air) so you need to have the unit positioned near a window or outside door.