Snoring and breathing problems in sleep affect more than 1 in 10 children worldwide, and are usually managed with surgery (removal of adenoids +/- tonsils). This study will determine if less invasive, low-cost, anti-inflammatory medications (nasal steroid spray and chewable tablet, montelukast) will help to reduce airway swelling, SDB symptoms and surgery. Using an innovative adaptive study design, treatment options can be continued, added to or switched to optimise response.