28 day tests

I am due to get a test at the local GUM clinic on Thursday which is 28 days post possible encounter.
I could go and get a DUO test at a private clinic which lists “Our standard DUO HIV Test results are available within 4 hours by phone, or in person. This includes the P24 Antigen and HIV 1 and 2 Antibodies. We can test 28 days after contact with a very high degree of accuracy.”
I went to the GUM clinic who said they do their normal tests and I think they said a PCR test as well, which was extremely sensitive.
I am starting to get confused as to where i should go or should i do them all.