Discussions of networked light switch wiring for US installations can be very confusing for those in Europe. The wiring is different, the wire colours are different, and the terminology is different.
Often the easiest way to add networked control to light switches in a European home is to add an in-line relay, rather than a networked switch. Several manufacturers make zwave versions of these on both European and U.S. frequencies, including Fibaro and Aeotech.
Vesternet, a retailer of home automation equipment, has a good FAQ on wiring European light switches to a networked relay. Worth a look if you’re dealing with European style two way switches.