My 5yr old suffers a lot with dry coughs sometimes lasting 2wks or more she doesn't have a high temperature with the cough. Any advice?

Yes. A recurrent dry cough such as you describe may represent asthma. You should see her pediatrician to discuss this and whether or not she would be a candidate for maintenance medications if consistent with persistent asthma.
Asthma . Has she been checked for asthma or acid reflux? Is the cough monthly or seasonal. Has she had a bronchoscope to look for other causes? Is she in preschool? Is anyone else in the hous affected (possible mold in the home). My first thought is asthma (allergy related) versus acid reflux. Have your child checked by her physician.