London Borough of Haringey ?
might be of interest to you, Obviously I don't know about the case you bring up I can believe that the children and parents were shown to be related by DNA although it doesn't mean that automatically disqualifies the child sex trafficking charge.
You might think that there should be some existing evidence to backup the presumed intent. If the parents were not criminally charged and convicted then it would make the councils grounds for their actions very shakey.
You seem convinced that the case was groundless and I wish you luck in persuing the matter, maybe there is some chance of involving the investigation of Harringey social services in your case. Its going to be tough for them to be fair especially after the death of a 17 month old child where they didn't do enough after which there must have been an attitude change and a desire to not make any more mistakes.
good luck with it, I hope it ends well.
On the positive side those children in care should be safe and fostered and adopted into happy homes, it is there well being that matters above all else.