Changed the battery.
I was a bit annoyed to hear a car alarm last night, and one that sounded like my car too, but looked outside and my lights weren't flashing so all seemed fine.
And then this morning it wouldn't remote unlock! Luckily housemate drove us to work.
This evening I checked the voltage and 7.5v 🤬
Oh well, it was sold with a spare battery because it's an Alfa, and these things happen!
Could be that it was standing for three days, or it's gone cold, or that I have a dash cam that switches off at 11.8V. So I'll switch that function to ignition switch and hopefully all will be fine.