The police can take action against you if you meet in larger groups. This includes breaking up illegal gatherings and issuing fines (fixed penalty notices).
You can be given a Fixed Penalty Notice of £200 for the first offence, doubling for further offences up to a maximum of £6,400. If you hold, or are involved in holding, an illegal gathering of over 30 people, the police can issue fines of £10,000.