Nest 3rd gen thermostat... hard wire to socket?

[Cocat2517]

Hi
Just fitting my Nest 3rd gen thermostat, it requires a 12v power supply, mains power is obviously too much and will kill it. Its located just above a double socket (ring main), is there any way of coming off this socket with a wire to power it?

Found this 240v to 12v reducer, what would be the best way of using this? With a FCU off the socket?

 

[Cocat2517]

Mains socket to an 3A FCU with 2.5mm², then FCU to 240v-12v reducer with 0.75mm², then reducer to Nest with 0.75mm².

Is this allowed?

Bit of a faff as opposed to plugging it in, but I wanted it hardwired so people can't unplug the Nest to use the socket for their iPhone chargers etc.