Long time mumsnetter but have NC'd as I do not want to be 'outed' if XH is lurking!
This may seem complicated and a bit waffley, but I am angry and upset and I do not know where to turn or where to go. I will try not to drip feed, so please get yourselves a cuppa and good luck!!
I have 2DC aged 11 and 9. Their biological father and I were never married and after a very stormy 4 years together (DV and EA) we seperated. He, however, was very lacsy daisy in regards to contact and would often let the children down last minute. Within a year of us seperating I had met (let's call him Steve for ease of this conversation) Steve. Steve and me had been friends for several years previously and had met my children in many 'friend' scenarios. We were together for almost 2 years when we got married. Sadly, and we both accepted this at the time, the marriage was not going to work because I did not love him anywhere near as much as he deserved. However, the children were happy with him and he was very much a 'Dad' figure in their life as their biological Dad had no want for regular contact with them.
Forward to 2008 and I receive a letter from a solicitor stating that biological Dad decides that he now wants contact with them and for them to go and live with him and his new GF 
is the understatement of the millenium!!! Obviously this not only shocked me, but panicked me to the core - this man, who had not wanted previous contact, even though I begged him to see his children, was now spinning a solicitor a huge sob story and I was afraid that I would somehow be forced to faciliate this. Social services and CAFCASS were involved as I told them that as the children no longer 'knew' him, I would appreciate some time for them to slowly restart contact and regain some of the trust that they (and obviously I) had put into him. A long drawn out court case ensued, with a lot of threats from his side and CAFCASS and SS totally on my side. The main threat that concened me the most was that if anything should happen to me, (I had had an accident in 2007 which had left me fighting for life) the children would automatically be placed with their biological Dad. Cafcass advised that they would get a 'residence' order in place so that if anything should happen to me, the children would remain in the care of Steve. Which, at the time was the best option as the children were in a stable environment. This order, in turn, gave Steve parental responsibility and would therefore negate the need to apply for adoption of the children.
Forward another 12 months and bio Dad had failed on several occasions to turn up for contact and had failed to attend the final hearing. It was decided (by the judge) that Bio Dad was to have no further contact.
Now, this is where it starts to get complicated (if you aren't already totally confused!!) Myself and Steve have since split up and as predicted it has been dealt with very badly on his part as he cannot accept this. This split has happened a little over 12 months ago and I am still hounded day to day. He will try to use the DC and when he has contact (which he maintains a very regular contact schedule that works very well for all parties involved) tries to (unsuccessfully) gain information from them about my current situation. This is very upsetting - more so for my eldest DC - as understandably, he feels like he is being put in the middle. This has come to a head when this week, Steve has taken it upon himself to apply online for a secondary school of his choice. This school was neither my child or my choice and she is absoultely heart broken that she has had no option over this. Naturally I contacted the education board and the admissions department at my local council, both of which have told me that Steve made them aware that he had PR of the children and he was able to do this. I have to add that they have been very supportive of me and have currently placed his apllication on hold pending investigation.
The order that was given several years ago, was (or at least I was led to believe)to only ever be enforced, should something happen to me and NOT to give sole residency regardless of the current situation.
As we are to be divorced within the next 3 months (hopefully!) the children would then no longer be classed, legally, as his 'step-children' so would this order even stand at all? If he does have PR how (if I even could) can I get this revoked?? He is making my life hell and has now started threatening all sorts regarding MY 'contact'. It's a pretty unbelievable situation that I never thought I would find myself in. I really need advice and have no idea what to do next. He isn't the Bio Dad and yet he seems to hold more cards than if he was. I am exhausted from talking to people that are not helping me and I seem to be going around in circles. If you can help please, please do.