Christopher Mark Leslie, son of Desmond Leslie, second son of Sir Shane Leslie, 3rd Baronet. I believe was heir to his brother, Shaun (named as Sean in the death notice), who has not claimed the title. Mark Leslie's son Luke is heir to his uncle now, if I am correct.
The Castle Leslie and Glaslough estate is still in the family, but in a trust, and is a hotel run by Marks sister, Samantha.