Thats correct re the cylinder stat not calling as it then switches 230V to the grey wire via the stat satisfied contact (2) which motors the valve to CH only, (port A) BUT/AND if HW is not selected ON then the HW OFF contact supplies this 230V to the grey wire, in other words the cyl stat SAT contacts and the programmer HW OFF contacts are wired in parallel, its possible that there is no wiring from the (programmer) HW OFF contacts wired to the terminal box or the programmer has a defective HW OFF contact. Still doesn't account for the noisy operation of course, you could remove the actuator, set the programmer etc to whatever causes the noise, open the valve manually to the corresponding position and see if still noisy.2. Central heating only works when HW is also on from controller. This does not mean HW is called by cylinder, just on from controller. My understanding is that when central heating and hot water are both on from controller, hot water cylinder thermostats decides if there is need for hot water or not, and if there is no need for hot water, then it sends signal to value to move to central heating only. I am looking for wiring diagram to allow for this function. All this will not happen if hot water is off from controller. This is how system was working previously.