New regulations requiring those who *operate* sea/air/rail services bringing people to UK to provide certain public health information (eg 14-day quarantine) to passengers or risk fine/prosecution. No powers to punish passengers for breaking quarantine legislation.gov.uk/uksi/2020/567/… 
And here are the regulations which require people arriving from outside the UK to (a) inform the government of their address (b) self-isolate for 14 days when they arrive. Another super-complicated list of exceptions to digest legislation.gov.uk/uksi/2020/568/…
Serious enforcement powers for the police, including (a) power to (a) direct a person back to the place they are self-isolating, (b) remove them back, (c) remove to "accommodation facilitated by Secretary of State" or (4) prosecute for failing/refusing to carry out requirement /3
And as with the local lockdown regulations there is a fixed penalty notice regime which can rise to £3,200 if there are repeated breaches /4
