People living with chronic obstructive pulmonary disease (COPD) may experience worsening of symptoms such as shortness of breath, cough and wheezing in addition to changes that may be expected for having COPD. The worsening of symptoms is called exacerbations or flare-ups and can be debilitating and frightening, requiring additional treatment, often with azithromycin. This is an antibiotic medicine that also has anti-inflammatory properties. It is prescribed as long-term prevention to reduce the risk of flare-ups. Some people may be affected by side effects from azithromycin. Antibiotic resistance is another concern, especially when using azithromycin for prevention rather than to treat active infection. It is currently unclear as to whether people should be advised to stop taking azithromycin once COPD has stabilised, or to stop it over the summer when fewer flare-ups happen. It is also not known if azithromycin is more effective in some people or more likely to cause side effects in others. Given these uncertainties, it is challenging to know how best to use azithromycin in managing COPD. Azithromycin is a valuable antibiotic, and should be prescribed where it has benefit but avoid unnecessary side effects and reduce the chances of bacteria becoming resistant to it. The purpose of this trial is to be able to gain results to answer these questions, and to establish the effects of stopping azithromycin in people whose COPD has stabilised, who have been taking it for at least 3 months. This trial will compare continuing azithromycin with stopping it completely, or stopping over the summer only, continuing over the winter. The investigators will compare the effects of these three treatments in the trial on flare-ups, symptoms and quality of life, and find out what factors may affect how individual participants respond to them.