From P&O Q&A
Adequate tests include over the counter tests, providing they meet the criteria below. NHS tests are now only issued for those in medical need. However, if guests have any remaining NHS tests, these would be accepted. Accepted antigen tests include:
Rapid antigen test
Viral antigen test
Antigen Lateral Flow Fluorescence
What is acceptable proof of my negative COVID-19 test result?
Guests will no longer need to provide a test certificate, however, they will be asked to confirm the test has been taken, with a negative result, for them and each member of their party as part of their pre-boarding health declaration at the terminal.