Is it a must to earth the central heating radiators in the house? Is
the Green wire that comes with the main true earth? Thanks.

Metal central heating pipework requires supplementary bonding in the
bathroom. It is may also be earthed through other points, where it contacts
main equipotentially bonded services, such as a non-disconnected filling
loop (to water), or a gas boiler (to gas pipework). There is no harm in
bonding it to the main terminal as well. There is no need to bond every
radiator separately. Indeed, if the pipework is plastic, this will reduce
the safety of the installation.

Christian.