You should contact your local Neighbourhood Policing Team via 101 and provide them with as much detail as possible. For example, if known, who the youths are and where they're from, descriptions of the youths, vehicles and times when they tend to ride.
Community Support Officers are a valuable source of information and the team may be aware of other incidents or the identity of the youths involved.
The police have a number of powers to deal with the use of such vehicles, these include the seizure of the vehicle under section 165A of the Road Traffic Act 1988 (Power to seize vehicles driven without a licence or insurance) or section 59 of the Police Reform Act 2002 (seizure of vehicles used in manner causing alarm, distress or annoyance).