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Thanks everyone. Doctors didn't measure her peak flow as they said she was too young at 5 to be able to use it properly. In answer to Eve's question she is very active and is always running about, we sometimes go on long walks and she can quite happily cope with 3 or 4 miles without showing any sign of breathlessness or being worn out. That's why I find it all so mystifying.
This cold has actually gone away without any more night time coughing in a couple of days.