When we got our boiler replaced, we asked the heating engineers to put in an extra room thermostat under the stairs in the future node 0. (Of course, there was nothing under there at that time and they thought we were mad.) However, they did install it and so we had two thermostats, either of which could "call for heat".

The plan for control is to turn down the thermostat that is in a sensible position, so that it'll only call for heat if things go horribly wrong. Then we're going to replace the other thermostat with an AD10 X10 din rail switch. When you take the front off, the room stat has three terminals Neutral, Live, and Switched-Live so it's a simple matter (cough I only blew the fuse on the heating once!) of connecting these to the Live In, Neutral and Live Out on the AD10.

Our brief tests show that this works. Now we just need to persuade our electrician that it's a good idea.