stop parking for free on our road

The residents of northview crescent nw10 want for people to stop parking for free on our street. when confronted and asked to leave the spaces they turn and tell us to "fuck off" and "what are we gonna do about it"...therefore we are doing something about it.The school have told the parent's not to park on the resident bays, but the keep on parking on the bays, that we pay good money to park on. The resident would like for the right entity, to install cameras or send regular parking official to this road, because in 2 years at this residence i have seen no parking attendents visiting the road.