How can I reprogram remote locking on Fiesta Mk4?

All of a sudden stopped working. Works via the key, but not through the remote. Changed batteries few months back. Didnt think it was the battery but changed it anyway but no effect. Checked Haynes manual but doesnt seem to give advice that is suitable for my car (ie. turn to position I and then back to 0 and the clock should stay illuminated for 30 seconds, which doesnt happen in my case and just goes off). Also talks about an transmitter with a light. Thought my remote might be the transmitter but has no light so must be on about somethin else.

Any ideas please??