From this, it looks like you just need an "ID card." They aren't overly clear though. Your best bet is to call up a travel agent, they're sure to know.
No. The visitors' passport, formerly obtainable at post offices and valid for one year for travel to a number of European countries, has been abolished. The only country where a passport is not required of a UK citizen is the Republic of Ireland and then only under certain circumstances, the principal one seemingly being that the flight originate in the UK/ the Republic. This accommodation of UK citizens is not without its own amusement. I once lost the ID slip issued by the carrier. The official at the gate on my return to England refused to let me in, though I showed him my UK passport. I had to go over a negotiate my way in through passport control!