s plan heating and also underfloor heating

Don't forget that each underfloor zone will have "stat", that also may have a temperature sensor in the floor, so some method of installing the sensor will be required if fixed wiring is plastered in. I normally run a 20mm plastic flex conduit down from the stat position to the floor level. (c/w draw string).
The pump in normally part of the manifold, but a cable from the manifold/valve control box to the boiler will be needed to control the motorized valve feeding the u/f system
Hope this is of some help

 

If its an 'S' plan the plumber will be using one or more valves in the pipework, each with a 5-core flex that also needs to be wired in to the wiring centre. I assume from your description you are using a wiring centre? The underfloor heating is just an extension of the CH if its a wet system and he will have valves on the manifold controlling that. Don't get too carried away with wires to the roomstats. If they are digital stats they won't require a neutral wire, just supply and switched live, so a twin will be fine.

 

Some UFH stats use cat5e, so check before first fix!

The UFH controller/wiring Centre is fitted by the manifold, to allow actuator leads to connect directly. This controller has volt free contacts to fire a boiler. You use these not to fire a boiler, but to open the extra two port zone valve. This zone valve then fires the boiler. Usually, two twins from your UFH controller to the cent heat controller.