I thought it was cold yesterday but this morning it really is. According to my phone it's currently "-4°C, feels like -8°C" — and does it ever! The heating has been on for a couple of hours and doesn't seem to have made a dent.
Some good news, however, is that I have seen one of the great tits back on the bird feeder again this morning so I'm really happy about that. It would be such a shame if they stopped visiting altogether.