Grandparent acess rights

[unhappy]

My sons grandparents are taking me to court to try and obtain access. I am not happy about the situation as the grandmothers recent behavior has been totally unacceptable. I recently moved away with my new partner and at no time did i tell grandparents that access was no longer allowed. Within two days she was threatening to have me hunted down, that she had paid some- one �200 to do so, phoning my 8 yr old son at midnight to name but a few things. I cant accept this behavior and in actual fact my eldest son is undergoing treatment from a phychiatrist and some of the things he has told her regarding his grandmothers behavior are frightening. Also in the past i have had reason to have a solicitors letter sent to her regarding my youngest son. She refused to have him at her house, constantly left him out of things including holidays, gifts, etc. This was extremely upsetting for my son and myself as a parent. Thier father ( grandmothers son) has recently denied he is father of youngest son ( totally untrue) and i have a feeling that this may account for her neglect of him. The father and myself were not married. i really want there to be no more access. How do i stand as regards the law.