Firstly, if you ex partner is refusing to let you see your son, and is being difficult in general then you should firstly, attempt to go to mediation to see if you can get some kind of agreement in place. However, in anticipation that this might not work, you would need to go to court and get a legally binding court order in place. This means that in the future, if your ex pattern attempts to do any of the same then you can make an application to have her held in contempt of court. The difficulty with this and the harsh reality is that if you go to court and she says you are doing this then Cafcass may become involved and want to speak to your son about the situation and that is not fair on the children, however, it is sometime necessary sadly. Ultimately as long as you have the child's best interest at heart then that will come out during any investigations. In terms of the child maintenance, no this wouldn't really matter. You are clearly looking after and paying for your child when they are with you so don't worry about this. Finally, in terms of the daughter. I am afraid that you don't really have any chance at all of getting parental rights despite your long term relationship with her. Parental rights can be very difficult to get even when all parties want this to happen. Sadly, this is the harsh reality, as you don't have any parental rights, the judge would not be able to order any contact for you with the daughter. However, hopefully the mother will eventually do the right thing and allow you to spend time with both children.
To find a mediator in your local area, use this site :
In order to apply to the court, you will need to fill out and send form C100 (copy attached) with a cheque of £215 payable to HMCTS to your local family court centre. Or you can ring the court and pay over the phone (or pay in person if you go directly to the court and pay at the counter). If you are on low income/have low savings you can apply for a fee exemption here:
Once you apply the court will list a hearing where you and your ex attends. There will be a family advisor there too (from Cafcass) and if arrangements can be agreed then a consent order will be drawn up.
I hope this information has helped. You can find a local solicitor who deals with this on the law society webpage which is;