A week or so ago I had a donation bag pushed through my door from the Air Ambulance Service (which is the umbrella organisation covering the Childrens Air Ambulance, Derbyshire/Leicester/Rutland Air Ambulance and Warwickshire\Nothamptonshire Air Ambulance).
Presumably they are allowed to do this because they run the Childrens Air Ambulance (which is national) - our local Air Ambulance is the Thames Valley & Chiltern Air Ambulance.
However, any donations go to the Air Ambulance Service (the small print says "a minimum of £105 will be paid to the Air Ambulance Service for every tonne of clothing collected"). There is nothing claiming that the collections outside of Derbyshire/Leicester/etc. would be dedicated to the Childrens Ambulance Service, for instance.