A 10-year-old boy with known asthma presents to the GP with increased wheeze and cough for 2 days, not responding well to his usual salbutamol inhaler (reliever). He uses a preventer inhaler (beclometasone 100mcg BD) regularly. His peak expiratory flow rate (PEFR) is 60% of his best. He is able to speak in full sentences. According to NICE/BTS guidelines, what is the most appropriate immediate management in primary care?