Gary, you've been told this before, but 6 months is what you need. Not two. So if you are working with professional porn stars (something I doubt), then you most definitely, unarguable, categorically ARE putting them at risk.
"What is a window period?
The ?window period? is a term used to describe the period of time between HIV infection and the production of antibodies. During this time, an antibody test may give a ?false negative? result, which means the test will be negative, even though a person is infected with HIV. To avoid false negative results, antibody tests are recommended three months after potential exposure to HIV infection.
A negative test at three months will almost always mean a person is not infected with HIV. If an individual?s test is still negative at six months, and they have not been at risk of HIV infection in the meantime, it means they are not infected with HIV."
http://www.avert.org/testing.htm
You are putting the whole UK industry at risk.