All you can do is to go to the court and explain as carefully and fully as you can, why you want to see your children. A father has a legal right to have time with his children. As you say ,you can't get legal aid as it can not be given to both sides in a family court matter.
I am sorry, but the fact that you have attempted suicide and have had PTSD will be used against you.
You can apply for supervised access to your children as a first step. This will be at a local children's center run by the council. The children will be taken to the center,which is like a play group with activities for children, and you will given time with them at the center. During your time with the children you will be monitored to see how you and your kids get on together. If this is successful you can move on to full unsupervised access and then having the children to stay in your house for visits. We had to go down this route with one of my grandchildren and her father.
Family courts are very informal and will do as much as possible to help, so do not be scared of them.