European Health Insurance Card - EHIC
Hope I am not duplicating the message about this card and its value. 
I have head this information before, only recently and again today in the Money Mail, reports of Brits being held hostage by foreign hospitals. Hospitals and clinics in cash-strapped countries are refusing to to honour the EHIC card and demanding cash
up front before treating accidents and illnesses which would normally be covered by the card. To reiterate, the card does not replace travel insurance, but should safeguard those needing urgent treatment which
would normally be covered free by the member country to it's own residents
- this can vary immensly, depending upon which country in which you are receiving treatment. The card is supposed to be valid in EU member countries plus Switzerland, Norway and Iceland. If you are at all doubful about the cover provided, then you should really
ensure you have additional travel insurance - I do 
Have a happy holiday!