You get a Large package for €399. This package contains everything from the Medium package, plus the following extras: installing a smart thermostat, installing a radiator fan (max 2) and installing LED lamps (max 4). The advantages of the Groot package are that you get a number of extras that you don't get in the Medium package. For example, you can reduce your energy consumption by installing the smart thermostat, and you can illuminate your home with the LED lamps.
Is it better to leave this to a professional?
It is often better to leave the installation to a professional, because they have the right knowledge and experience to carry out the installation properly. This way you can be sure that the installation is carried out safely and properly.