Don't you have to declare on a landing card whether or not you have had exposure to TB? If so, then you will be taken aside for a chest X-Ray at the airport. My feeling is that the right thing to do would be to book an appointment with a doctor now, before you leave, have the test, and then you can present the certificate giving the all-clear when you come in if need be.
TB is growing in the UK because of a number of immigrants who have not taken this responsible approach. While you are probably (hopefully!) okay, I think that it is best to be sure, both for public health reasons and your own peace of mind.
I hope your brother is okay.
Vicky