Hello there.
I have just joined this forum, and am in Australia. I am interested in this X-10 stuff and think I have an answer for you:
I made a transmitter that takes relay contacts from an alarm panel and turns on/off x-10 modules as per the relay programming. The on / off control follows the input. IE contact closed sends ON, contact opens sends OFF. The only disadvantage is that my little device plugs into an XM10 interface in order to communicate with the network. This may or may not be too expensive for you, but I am not quite sure how much these things cost over there.