There's nothing to worry about regarding 'fitness' for the UK CAA class 1 initial medical examination at Gatwick unless you declare on the medical questionnaire that you have, or have had a history of asthma. Not wanting to lie I declared a history of mild asthma and was made to undertake an 'exercise spriometry test' giving the CAA the right to charge an additional fee of £35 to run round the building for 6 minutes. I was completley unprepared for this and failed, and I wouldn't consider myself unfit. A few months later after sorting out some other issues I returned to Gatwick to re-do the exercise test (again at £35) which I passed after preperation.