With the Webbrick controller and the Webbrick  gateway there is more than one way to setup heating solutions, you could use the Webbrick to be remote switching and do all the logic in the Gateway or you could offload all the control to a webbrick, using the webbrick controllers scheduling abilities.

If replacing a simple heating controller and not attempting to extend its functionality, then the webbrick can provide more than the  equivalent of a time clock and programmable thermostat.

If aiming to control a large number of zones with multiple heat sources then the control may be best handled fully from the gateway.

There is still a middle line here where the valves are controlled by webbricks  using temperaure sensors to switch them on and off. With the Gateway controlling the temperaure threholds as required. The gateway can then respond when it sees that a valve has been opened and switch on the required heat source, based on cost and priority. i.e. The Ground source heat pump can be used in preference for demand to a single heating zone at any time, but if heating and hot water are both required then use Ground source for heated floors and Boiler for hot water.

Also to watch is the response times for heating, how quckly does the building heat up and cool down, I have seen one building recently where the insulation is such that it takes 2 days to drop by 5 degrees. With underfloor heating with large thermal mass, lots of concrete to you and me. It can take hours to raise the temperature by a significant amount. There may also be an over shoot where the underfloor heating still puts heat into a room after the system switches the zone off. The occupancy of the building will also affect how you heat it.

So in a building that has a large thermal mass and a reasonable amount of day time use, it may be most cost effective to run a ground source heat pump during off peak electricity hours (UK - Economy 7, Economy 10 tariffs) when the per unit cost can be 25% of the peak usage. Even if the building does not have heavy day time use, with good insulation the losses during the day may be more than offset by the reduced costs of getting the heat in to start with.

Also the heat demand priorities may affect the heat source, a modern boiler can reheat a tank of water in 20 minutes, this response time may not be neccesary during most of the day but with 3 or 4 baths required in an evening, that may be the time to prioritise the use of a boiler for hot water and leave the ground source doing heating.

[A little ramble but may provoke thought]