How will the EU travel ban affect Britons who have booked holidays?

Covid rules on non-essential travel will kick in for UK when Brexit transition ends on 1 January

British holidaymakers will be barred from the EU from 1 January as the European commission has indicated there will be no exemption for the UK from Covid-19 safety restrictions. What does it all mean for Britons with a holiday booked in 2021 – or sooner?