You need to interact with social services, calmly and clearly tell them it is your intention that you will do all that they ask to regain care of your children.
Make sure you interact with the crisis team, your GP and everything else that you can get access to, have therapy, get on a medication regime. If it isn't helpful, get it changed. It can take many chops and changes to get the right medication mix.
Ask social services for guidance-
• you want to know what steps they expect that you take to adequately prove that your children's needs can, and will be met by you and DH, in your home.
• Which information they want to be kept updated on, and by which way is preferable- email, call or can you just save it all for each meeting.
•How involved you can be in the children's daily care whilst the children are at their grandparents and if there are any things they'd specifically prefer that you weren't involved in for the time being.
Work with them, work with them, and work with them.
I do wonder how this all came about though, did the hospital make social services aware that you kept turning up? I'm just not sure how you got to the point where they turned up after so long