If an overnight stay in the UK is necessary before you can get transport back to the Bailiwick, then you and any travelling companion can stay in a hotel or guest house or at a friend/family’s residence or in your own UK property.
The self-isolation accommodation in the UK can be in a hotel or guest house – but you must stay 2 metres from all other guests and staff. You cannot use shared areas such as restaurants, bars, health clubs, sports facilities etc., even if you could be 2 metres from others.
The self-isolation accommodation in the UK can be staying with friends or family – but you must avoid any contact with the people you’re staying with and minimise your time in any shared areas.