How long ago did she move? Please confirm that there is no child arrangement order for contact.
I’m sorry, I’ve just noticed that you are in Scotland. The law is very often different in Scotland so I’m going to opt out for a Scottish expert.
Under Scots law the only way to deal with this is to go back to court. If you can't afford that, you may qualify for legal aid. A contact order that is rigid in its terms may be necessary as your wife clearly has a difficulty in sticking to arrangements. As your son is 13 his wishes have to be taken into account by the court, the court will assign a child welfare hearing and your solicitor will have to be fully appraised of the difficult history to the divorce. The court will take the view that you should bet contact unless there is a very good reason why not. Happy to discuss. I hope that helps. Please leave a positive rating so that I am credited for my time.