You can’t use these behind a double socket. These switches are rated at 10 amp. You can draw up to 26 amps from a double socket, and the circuit the sockets are on will be protected with a 32 amp breaker.
You will fall foul of UK electrical regulations if you try to install any 10A-rated relay behind a 13A socket. The potential solutions I can think of are:
Use a relay that has a higher rating that the socket in front of it (i.e. 13/26Amp). E.g. the Heavy Duty Switch. This has the disadvantage that the button on the socket will operate independently of the relay.
Use a 10Amp relay, but change the wall sockets to UK 3A or 5A sockets (these have round pins and commonly used for lighting). Example. But this is undesirable as nearly everything will have 13A plugs.
Alter your ring-main to create a new ring circuit just for the room you want to monitor. You could then use either a clamp monitor (e.g. The Aeon HEM) or a DIN rail device (example).