If you are a UK resident you are entitled to free, or reduced cost, state provided healthcare when visiting a European Union (EU) country, Iceland, Liechtenstein, Norway or Switzerland.
However to be covered you must bring a completed and validated E111 form. the Post Office will supply an E111 form - follow the instructions to get it validated BEFORE you travel.
Currently, the scheme is being effected via new plastic credit card size cards, rather than the paper A4 form that has been used to date. More details to follow.
The E111 scheme may not provide full medical cover, and therefore you may want to take out medical insurance also.