 Screening Visit At the screening visit, the information document will be discussed with the participant and written informed consent will be obtained if they agree to take part in the study. The following will then be performed: a general medical examination by a doctor; a pregnancy test for all females; lung function measurements spirometry, impulse oscillometry, reversibility to salbutamol; heart function measurements resting ECG electrocardiogram, echocardiogram where possible if not done in last year; vital signs oxygen levels, blood pressure, pulse; practice cardiopulmonary exercise test to confirm ability to cycle and to counter any learning effect from future baseline exercise test; baseline blood tests. Inhaler technique will also be assessed and confirmed adequate. Participants found to be eligible for the remainder of the study after these tests will proceed through a 1 week run-in period on their usual medications before coming back for the first baseline visit. Those who do not fulfil the study criteria will continue on their usual medication and their General Practitioner GP informed of any medically relevant data. Eligible participants will be provided with portable monitors to measure their own lung function, pulse and oxygen saturations at home twice daily to be recorded in a daily diary which will also include details of their reliever use and symptoms. This diary will be kept throughout the study. 