What legal options do alienated grandparents have?

If grandparents are not being allowed to see their grandchildren, they have the following options:

Try to ascertain why contact is being denied, and reach an informal agreement with the parents of the grandchild.

Invite the parent or parents to engage in a form of non-court dispute resolution such as mediation or arbitration to find a solution.

As a last resort, apply to the court for permission to make a Child Arrangements Order.