CEF AP28 alarm issue?

My CEF AP28 alarm control panel "24" light came on the other night and was beeping. We entered the code and the beeping stopped but the light was still flashing. This morning at 6am the house alarm was sounding on the rear of the property (not the front) and both control panels were dead. Can anyone give me any hints as to what might be the issue and can we fix it? We removed the battery out of the main unit and switched the mains electric off, but the alarm was still sounding so we disconnected the siren on the rear outside alarm box just so we don't get linched by the neighbours! Was a great start to the day :-)