Such sad stories from everyone - I'd like to just add, my XH left four years ago and I have managed to move on - in fact I've never been happier. I recount my stories these days as in a, you'd never believe what my XH did... normally over a coffee with friends etc.
What he did to me made me strong and this month I start a new job, in an entirely different field to where I worked in the UK, I did all my interviews in French and I beat 110 people to get the job. If I'd still been the sad little mouse I was when I was married to him I'd never have tried. But when he left and did what he did I thought Fuck you, I'll show you, and I have.
I've had amazing support the last four years from my brilliant family and friends and they have been amazing. They've taken me on holiday, they look out for me and the DCs, they've been fabulous. Looking at XH's ranty emails to me (because every six weeks or so I get an email where he goes off on one) he's really jealous of my life. He makes little digs about improvements I've made to my house, my holidays, my car, I love it when he does this, it gives me an insight into how shit his life is that he has to be jealous of me. His mad ranting emails give me great satisfaction.
How his life has gone...well he's still with the OW and they play happy families, she's ill a lot and he has to nurse her and look after her youngest DC (things he never did for me or our DCs) but he likes the adulation he gets from other people telling him what a wonderful guy he is for stepping up and doing that. She has no idea that once this stops, he'll stop doing it. He needs this adulation, he needs people to tell him what a great step-dad he is, it's his oxygen. They lurch from one crisis or drama to another, they both seem to enjoy that kind of life. It's not for me, he gave me enough drama when I was fighting to feed my DCs and stop my house being repossessed to pay off his debts.
However, so she can keep her benefits he has to rent a crappy little room in a house share so he can't live with her full-time. So a couple of nights a week he's sent back there to keep up the pretext of her being a lone parent. He went bankrupt and lost the flat he was awarded in our divorce because his name wasn't allowed to be on a mortgage. The mortgage was £310 a month and the flat was 30 mins from Liverpool Street Station and currently has a rental income of £750 a month. He has a flash car, and every product Apple have made, but it's nothing. If and probably when, it ends with the OW, that's all he'll have. He doesn't have his own friends, they're her friends and now he doesn't have his DC because he's dropped them like a lead balloon. He has got to be one of the most pathetic people I've ever met. I might even feel sorry for him one day...maybe.
So 
to all of you who are going through this now and you're hurt and bewildered and don't know what's happening, I promise you life will get better, time really is great healer and in four years time you will probably get out of bed every day with a smile on your face, grateful that your shitbag XH left you and like me, you'll probably be wishing he did it sooner, because life is too short to have devoted so much of it to a twat.