The list of EU+ countries broken down by a level of risk has been updated (June 30th, 2020)
Poland and Great Britain are considered as countries with a low risk at the moment.
As of June 30th, 2020 the Polish and British citizens and EU citizens with temporary or permanent residence permit in Poland and Great Britain can enter the Czech Republic without the necessity of having a negative PCR test and without the necessity to prove the purpose of travel.