 This study has two phases. In the first phase the investigators aim to recruit 224 patients through approximately 40 clinics in the UK and Ireland. One third of these patients will be selected in random to use the high dosage Seretide 250 Evohaler and two thirds will use high dose Flutiform 250 inhaler for 12 weeks. At the end of phase 1 the investigators will compare how well asthma was controlled between the two groups. 