Sadly it has become clear that the system installed is simply not going to work. So we are having it taken out, but keeping the Lossnay for fresh air.
Why on earth Mitsubishi would have a system supplied with dedicated controllers that have a thermistor in them, and a setting to use the controller temperature, but not actually support that, is beyond me. It does not even give an error, it shows a plausible, but wrong, temperature. But apparently they cannot support controlling from the controller, and so the two rooms off each system approach is just not going to work.
So now I have to start again with another air-con company. Maybe we'll get something before the summer.
All good fun. But they have sent interesting pictures of previous installations, which look cool.
So I'll post more when I have it...