Dillon has been with the company for 21 years and moves from his role as group operations director.
He will join group chairman and joint managing director Paul Collins.
Dillon’s first position with the company was in Poole as sales manager of the group’s Land Rover showroom.
He soon became the Land Rover brand director before taking responsibility for all brands in the group.
Peter Wood, joint MD, commented: ‘When Paul was appointed group operations director, his challenge was to pull the group together, ensuring that best practices, operational policies and standards of customer service were applied consistently across all our brands and branches.
‘It wasn’t an easy task as Westover had incorporated a number of other local businesses over the years, bringing a variety of cultures and working methods to the group.
‘However, Paul, supported by the rest of the board, has worked tirelessly to achieve a cohesive group, with tremendous success.’