 This study is a multi-centre, randomised, double-blind, active-controlled, parallel-group study, in male and female subjects who will be assigned into 1 of 3 treatment groups based on 1:1:1 ratio. Following a 2 week run-in phase all subjects will receive treatment for 1 year 52 weeks followed by a final follow up 2 weeks after their last visit, during this time subjects will be required to attend 10 clinic visits while the final follow up can be completed by telephone. Throughout the study subjects will be assessed on a mixture of symptom based measurements as well as lung function tests to monitor their progress in the study. 