Just got our "Important Pre-travel Information" guff from Eurotunnel.
On 1 July 2012, a new legislation came into force in France. All drivers of a motorised land vehicle, excluding mopeds, must possess a digital breathalyser or an unused (and immediately available) breathalyser kit which conforms to NF standards. This rule equally applies to vehicles registered outside France. Only vehicles fitted with Breathalyser Interlocks are excluded. Failure to carry a breathalyser in your vehicle will NOT incur a fine.
Oh and sorry, I know it's been asked before.