 Study visits Prior to participants attending for their first baseline study visit they will be asked to only withhold their short-acting reliever inhaler for 6 hours. Participants will not be required to withhold any long-acting bronchodilators for study visits as we are assessing any effects of the beta-blockers in addition to these standard treatments and we will have confirmed the diagnosis of COPD at the screening visit. Diary cards will be reviewed and the following measurements will be recorded at visit 1: resting lung function impulse oscillometry, spirometry, whole body plethysmography; resting ECG; vital signs; St Georges Respiratory Questionnaire disease specific quality of life questionnaire; blood sample BNP, Galectin, CholesterolHDL, Creatine Kinase CK, Potassium; cardiopulmonary exercise test. Provided the participants measurements still correspond to the inclusion and exclusion criteria for the study, they will be randomised to one of the two beta-blocker treatments: Bisoprolol 2.5mg daily for 2 weeks, then 5mg daily for approximately 2 weeks OR Celiprolol 200mg daily for 2 weeks, then 400mg daily for approximately 2 weeks. Beta-blockers will be up-titrated at home after 2 weeks with advice about contacting us if side effects develop. Participants will be contacted both before and after this up titration either by telephone or email. However, if adverse effects occur on the higher dose, then participants will be allowed to drop back to the lower dose for the remainder of the study period. At the end of each treatment period, study measures will be repeated as above. After visit 2 participants will have an approximately 1 week washout period prior to being given the alternate beta-blocker treatment. 