Just thought I'd share this- its an excellent site. You'll find guidance on how to co-parent with very difficult mums, alienation, and there are excellent guides on how to approach the court process. You can call them for advice and there are reams of free downloads, and lots of youtube videos which helped me a lot. They even have people on hand to call if you're struggling, highly recommended for anyone no matter what stage you're at.
Home - The Nurturing Coach
A dedicated service for victims of parental narcissistic abuse UK, including alienaiton, co-parenting and legal abuse through the court system UK
thenurturingcoach.co.uk