[Solved] In desperate need for help!

Hey, sorry this will probably be long but i will try to cut to the chase. My husband split from his ex over 5 years ago they had 2 kids together (aged 2 and 3) dad had residency for a year while mum sorted her self out, she then wanted the children back and we where unsure of our legal possition to stop her. (I had been caring for his children plus my own child for a year as hubby worked full time) kids went back to their mums 200 miles away from where they where born and their dad lived.
There was a verbal agreement in place where we had the kids during school holidays and take them out for birthdays, days out and ulternate xmas days. As well as regular contact via skype and phone.

As the years progressed we became concerned for their welfare but because of the distance and their mums hostility towards us (nothing too bad but she would just constantly critisise our parenting and constantly ask for more maintanance money)

We found out that the children have been involved with ss which we are now trying to optain the historic records for. The police had been called out to the childrens home several times due to their mother and step father going through a break up. We had children for contact and felt they would be at risk if we where to return them. There is alot of other factors to this (she hasnt had them medically seen to in a very long time, 3 years of headlice, school performance dropping etc) their mother lies and point blank refuses there are any issues. We sent her a letter (very polite and saying we still want her to see the kids but due to the abuse we feel they would be best with us) anyway. A series of phone convos i had recorded where the mother and her partner have verbally insulted me and threatened me. The mother even made the children cry as she tried to manipulate them on the phone. She also said on the phone that "everything you said in the letter is true but thats not enough to take my children away" "things are better now and im trying to do what i need to tp protect them" anyway. It went to a directions hearing where i felt the judge was completely biast towards the mother. He refered to her response to the c100 where she wrote a lie about how we broke up . the judge took her word for it and didnt even give me a chance to respond. He deemed the children should return to their mothers care and we should go to mediation with another court hearing in a few months. Cafcass had not spoken to the children before this hearing and they were both very upset about having to go back to live with their mum. We are now waiting for her to sort mediation out as she will get legal aid and we cant afford it as my husband is on a low wage and im a student. There is so much info to include in our case im so confused as to how to word it all and how to put it all together. We have drs letters, phone convos, texts, photos. She has also tried to get us to trip our selves up with our story (obviously so she can use that in court) she is manipulative but how do we get that across? Her aggressive partner is now threatening us with court for slander against him too.