The central heating engineer, Ian Hosegood, came this morning. It turns out the problem was indeed with the Siemens wireless base station (wall-mounted next to the boiler). It was showing the radio link to the living room thermostat as active, but the relay to the boiler/pump had not tripped. This is the bug in the device highlighted in the post I mentioned. Ian switched it out for the Honeywell CM927 wireless programmable room thermostat and upstairs relay box.
Finally, the central heating is working again.
In passing, Ian observed that I seemed to have a flat rear tyre (my car parked on the drive outside the front door). At the garage they found the screw causing a slow puncture - fixable; the other rear tyre was low-tread so had to be replaced. With the water pump failure last Friday, this has been an expensive few days.
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Clare and myself visited my mother this afternoon - here's one I took with her while Clare was at the cafe getting us all hot drinks.
