Planet Devices is not only cheaper kit, it is easy to install as it's a dry installation - it's not necessary to cut into pipework to install probes and meters. This saves the engineer time and the homeowner money. It also gives access to the ability to remotely alter some of the settings which the two alternatives that spring to mind don't. And lastly I like working with a local company (Planet Devices are based in Plymouth, we're near Exeter) that are going places.