Your test socket must work or none of your other sockets will. When you remove the faceplate do you have dial tone on any other sockets in your house?
If you don't have dial tone, put a small amount of WD40 or similar on to a phone plug and work it in and out of the Test socket half a dozen times. Then try again.
Edit - No offence to you IANTE, I know you are one of the clued up ones.
