If you are installing underfloor heating then you would install a wiring centre at each manifold. The wiring centre would provide the outputs for the boiler, pump and valve as well as the individual zone output.
If you are installing radiators, you can wire directly from the thermostat to the valve - and use the end switch in the valve to operate the boiler. Alternatively, if your valves are located in the same location you can use a wiring centre to simplify the wiring.