Update 2021-08-10: According to FCDO information, several classes of visa holders will again be permitted entry if they are fully vaccinated and have applied for an entry permit. Additionally, travellers from high-risk countries like the United Kingdom must quarantine for 14 days in a government facility. Restrictions apply for restaurant visits, indoor and outdoor exercises, depending on vaccination and test status. Likewise, gatherings are limited to at most five participants. For further details see the link below.
FCDO (1), FCDO (2)