You dont need to bring your chest xray if u dont want to as they can do that for you in the airport or once u are registered with ur GP here in the UK and It is stated clearly on the UK border agency website,that they require a TB screening for migrants coming for over 6months and one of the quickest test to know this is to have a chest xray.
http://www.ukvisas.gov.uk/en/howtoapply/tbscreening/
What is TB (tuberculosis) and why do we test for TB in some countries?
TB is common in the countries in which we test. It is an airborne infectious disease which can be spread by close contact with other people. The UK wants to encourage greater awareness and treatment of TB in the countries in which we test, as well as protecting people in the UK. Being tested before you travel also means that the arrival procedures in the UK will be much quicker.
Why are you only screening migrants coming for over 6 months?
Generally people must be in prolonged contact with someone with infectious TB in order to catch the disease. Those coming to the UK for more than six months present greater risks to public health than short-term visitors. It would not be practical to screen all short-term visitors for TB.