I've tested your suggestion of using a queue with the 'no answer' option and it works! The line is not answered and if an extension is registered it rings.
What I can't figure out if its possible to use a Fail Over Destination after say 30 second? I've tried setting the Max Wait Time, but this doesn't seem to work. What I would like to happen is after a period of time the call IS answered by voicemail.
Thanks again,
Peter.