Hi there Dad72 🙂
I understand that you cant discuss this in too much depth and thats fine but it does make giving the right advice a little difficult....however I shall do my best! 😉
Ak57 was exactly right in talking a bit about family dynamics and recommending Mediation, however as you dont feel that's an option lets talk about your other options.
Firstly do you have Parental Responsibility for the children. As they were all born before December 2003 you would need to have been married for this to be the case. You would need this to apply for custody.... but if you dont have it you can apply for it alongside the Residence Order.
As there has been a breakdown of the relationship between the children and their mother and the step father, the fact that you used the word "need" to leave and you talk about their safety, I'm assuming that there are safeguarding issues and the children are at risk. If this is the case then you would need to apply for a Residence Order and this is done with the C100 form and also a form C1a as there are safeguarding issues involved.
Do the children come and stay with you on a regular basis? I ask for two reasons.... Firstly, this would be helpful if you were to apply for Residency. Also if they stay over with you and you have Parental Responsibility you might consider just keeping hold of them instead of returning them back to the mother. This can be done but if you were to consider this I would advise you to telephone the police just to make sure that they wouldnt become involved if the mother called them. Generally if both parents have Parental Responsibility and there has never been a Residence Order granted to either parent then both parents have equal rights. This course of action would also mean applying for Residency and this would need to be done very quickly, in fact you could apply to the court to hear your case as an emergency in which case it would happen in days... This would prevent the mother from applying for Residency to get them back!
You could consider a solicitor or you could self represent. A lot of Dads take this route and it is doable. Solicitors charge the earth and a case could cost thousands! There are a couple of ways to approach this, you could do it all as some do, or you could self represent but employ a barrister for the final hearing. Alternatively you could use the services of a McKenzie Friend, they charge a small amount for their expenses plus a little for their time. My son recently used one and he charged £150 for 3 hrs, helped with the statements and liased with CAFCASS and the other sides solicitor.
CAFCASS are a court appointed body and are responsible for drawing up reports for the court. They usually have a background of Social Work but they only get involved in that context. Otherwise outside of court you would deal with Childrens Services who are also asked to furnish reports for the court.
The court process can be a long drawn out affair but on average I would say that there would be 2/3 hearings and it would take around 6 months but this is only a very rough guesstimate! Different areas differ widely.
As your children are all above the age of 11 then they would be interviewed about their wishes and this would be taken into account.
The more information you have about the childrens situation the better, if there has been police or Social Services involvement then that will be bought up in court and could work to your advantage. If there is a history of drug use by the mother and step parent then you could ask for drug tests. If you intend to apply for custody then you will need to back up your claims of the breakdown in their maternal relationship. Courts dont like to move children from their home environment, school etc without good cause.