If you tell them you have "chest pain" you will probably not have to go to Flight Screening. Ever...
Seriously, what on earth are you asking?
If you're sick with
(Vomiting, chest pain etc)
do you really want to be "allowed" to go to Tamworth and have your one shot of getting in, when you're feeling like that?
Or do you mean "will they still expect me to attend Flight Screening if I'm suffering from an illness?" - if that's the case, I'm sure they won't "make" you attend, though it may be a wait until the next opportunity comes up.
Come on, prospective military aviators, show some common dog!!