Thanks - I have now added an extra mate to limit the movement of the ball as well

Brilliant. If you get the chance to upload a tutorial on how to make these, I would really appreciate it. Thanks, KR.

It really isn't hard at all to do - there are two main mates. The first is a concentric mate between the ball and liner, and the second is an advanced -> limit mate which limits the angle between the flat face on the ball and the flat face on the liner