A 70-year-old ex-smoker presents with exertional dyspnoea and chronic cough productive of sputum. Spirometry shows FEV₁/FVC ratio 0.55 and FEV₁ 45% predicted. He has had two exacerbations needing oral steroids and antibiotics in the past year. According to the COPD-X recommendations, which of the following is the most appropriate maintenance pharmacotherapy?