Narcissistic ex refusing to leave my home

Hi I am in the UK so asking for some advice please.

My relationship broke down with my ex a year ago just past a year now, the list would go on for hours of all the things his done. Affair 4 months long, messaging and meeting another 3 woman, lied about having a driving license for 3 years driving children around I only found out as had a letter from 'his' insurance company car was fully in my name, stealing, lying, 'forgetting' every birthday of mine, refused to provide anything for the children until he could afford it, basically the most self centred vile man I have met personally and this is not half.

A year ago I snapped with driving licence and insurance more so as it actually involved the children I had not loved him in a why but easier just to live my life as anytime I brought anything up even the cheating he would find a way to make is sound like if I had just done etc he wouldn't have done it. ( I am a fool that I know now)

This man has no family his sister won't have anything to do with him he burnt his bridges there around 3 years ago no relationship with his dad he punched his dad years ago repeatedly I only found this out a year ago and his mum passed away 5 years ago, no friends and I mean none one bloke he would go watch football with and no money gambles or spends it god knows where.

When he moved in to my home we arranged an informal arrangement for him to be here and contribute which he rarely has done. I asked him a year ago to leave gave him a couple of months as I don't think I could see someone on the street, each time it came for him to go I would have tears I am on streets have no where have no money etc. so I am in a revolving cycle leave yes I am leaving get there he doesn't his stuff is packed literally his clothing I am getting to the point of just throwing it out but he threatens if I do his taking the children (2) and he won't return them as I can't tell him when he can see his kids.

I am being forced to live with a man I have put up with more than any sane person would have done, he is refusing to leave and I know for fact he has nowhere to go.

I am considering getting a legal letter to get him out will this work can I call police he isn't violent towards me but is threatening with words

Any help please as I am getting desperate