hey potsy,
a bit long winded but i'll explain,
its never happend to me but its happening around me at the moment, my boyfriends mum left him n his 2 sisters 6 years ago after having an affair they all stayed with the dad but he banned them from seeing their mum (my b/f didn't want to through choice) but the girls did want to see her. anyway a few months ago his youngest sister who im really close to turned 18 and decided she wanted to get in contact with her mum and now sees her regularly, their dad went mad and said she was a traitor to him and said she didnt care about his feelings n all that rubbish he told her she wasnt to see her but she said she was an adult now and he couldnt stop her so he said she had to choose him or her mum so she chose her mum and he told her to move out and not to speak to him again and they havent spoken since.
she is now living with her boyfriend and his parents whist her mum sorts her out a room in her new house and has never been happier, her mum seems to care loads about her and they have spent the past few months catching up on the 6 years she was to scared to speak to her mum because of what her dad would say, my boyfriend still doesnt want to talk to his mum but not because his dad says. his sister says though that in the end it will be him who loses out as when she has children and gets married it will be him who won't be there to see it all.
i find their dads attitude appalling he is nothing more than a bully and in my opinion has no right to tell them who they can and can't talk to especially their own mum but I guess thats what happens with divorce.
sorry ive waffled on but all i can say is just think about the good relationship you now have with your mum after the years you were apart and your dad has only got himself to blame and will be the on who loses out in the long term.
good luck for the future clare xx