2 seconds after publishing the first post i find this in an email from the RHA. The following information is taken from the RHA’s Summary Guide to Smoking Ban at Work. Thanks to the RHA.

Can drivers smoke in a works vehicle? Yes, unless the vehicle is used by anyone else at any other time. The regulations will require enclosed vehicles to be smoke-free at all times, if they are used:a. by members of the public or a section of the public (whether or not for reward or hire), orb. in the course of paid work by more than one person, even if those people use the vehicle at different times, or only intermittently. Intermittent use by other people would include the intermittent use of the vehicle by a worker such as a fitter using the vehicle for testing purposes. If there is regular or intermittent use of the vehicle by other workers, then the vehicle must remain smoke free even during any daily rest break taken by a driver in a sleeper cab.

Again it shows that even drivers in sleeper cabs cannot smoke in cab, even after hours. To read the RHA’s complete Summary Guide click the following link; http://www.rha.net/adviceandinfo/plonearticle.2007-06-28.4094792133  The guide also states; Who will inforce the regulations? Local authorities will enforce the new regulations and enforcement functions can be transferred between enforcement authorities.