The new 100km exemption applies to:
Vehicles or vehicle and trailer combinations with a maximum weight of 7,500 kg which are:
•used to carry materials, equipment or machinery for the driver’s use in the course of his work and when driving the vehicle is not the driver’s main activity
•used to carry goods and which are propelled by natural or liquefied gas or electricity
•vehicles used to carry live animals from farms to local markets, or from markets to local farms or slaughterhouses
As from 2 March 2015, these vehicles will no longer have to be fitted with tachograph recording equipment and the drivers will not have to comply with EC drivers’ hour rules. Instead, drivers of these vehicles must meet GB domestic drivers’ hours rules.
You can read more about these changes here :
https://movingon.blog.gov.uk/changes-to-tachograph-rules-for-local-journeys-2/