In reply to Cai:
(£1,000,00 per year per air ambulance) divided by (7,000,000,000 people abroad) gives 0.014 p per year per air ambulance per person abroad.
Seems pretty compelling if you can get the cost of collecting it down to less than 0.01 p per person per year.
Edit: Beaten by another poster whilst doing maths in my head.
Post edited at 16:40