Both the prostitutes and the kerb-crawlers are committing criminal offences by carrying out these activities. You need to inform the police, obtaining as much information as you can about the people involved, the names of those believed to be soliciting and the vehicle registration numbers of any suspected kerb-crawlers. However, do not put yourself at risk. If in doubt, contact your nearest police station via 101.
Warning letters, injunctions and prosecution are some of the tactics used by police and other agencies in an attempt to combat offences such as these.