I bought a couple of butterfly valves made by Eurofly;
I'm intendng to motorise them with a stepper motor in the style of the Depac valves.
The plan is to use two valves, one on the inlet and the other on the outlet. Load control is done by using the valves in opposition (open inlet and close outlet or vice versa), whilst water temperature is controlled by using the valves in tandem (open both inlet and outlet together). The aim being to minimise water consumption.