80's Film Where 'Old Man Dermott' Uses Witchcraft to Avenge Grandaughter's Death

by Debbie
(Luton, England)

What's the 80's movie where a young teenage girl runs out in front of a man's car and is killed by accident, and her grandfather (who they refer to as 'Old Man Dermott' or something uses witchcraft to get revenge on the driver who killed her?

In one scene, the driver has a seance with a medium to try and stop the grandfather but he finds out about it and bursts in the room and stabs the medium.

I was really impressed by the film and would love to see it again. Thanks!