While you wait for answers, we may have found some information which could help you.
Click here for Valve Test Pressurehow do i remove the cap from a myson 2 way trv?
myson trv 2 way?
How can i over-ride the Myson thermostat's PIN number?
apollo myson 50?
My Myson thermostatic radiator valve is not working and will not open?
how do i remove plastic top of myson thermostat?