Just wanted to say thanks to the people that responded to my query the other day. I took ds to the doctor who would not diagnose asthma and told me that all children get lots of coughs and colds which they grow out of. I pushed her a little and she did prescribe ventolin. We have been using it for a few days now and I can't believe the difference in him. Although he has developed a cough and cold, his energy levels have gone through the roof. He is still coughing through the night, but he must generally be taking in much more oxygen as he has sooooo much energy. He really is like a different child.
Thanks again to all who helped.