Boris Johnson says the public must not let businesses down when they reopen on Saturday.
Bricks and other missiles were thrown as officers tried to disperse the gathering in west London.
Portuguese leaders say the country's exclusion from a list drawn up by the UK government is "absurd".
Lockdown measures in Wales are still in force as pubs open in England on Saturday.
Citizens Advice says people are "increasingly concerned" about job losses as the lockdown eases.