It's complicated your friend's situation, but I understand your/her urge for quick reassurance.
Firstly, all the ins and outs of divorce read Family Law Made Simple by Gordon and Slater. It explains the difference approaches (and the divorce procedure). It certainly calmed me down when I read it! Litigation via solicitors/barristers is shockingly expensive, so a DIY divorce may work for her. In which case, that book, and Wikivorce, will be a God-send to her.
If he will admit to adultery, then I gather he has to pay the costs of the court fees. These are a few hundred pounds. If not, she'll have to divorce him for Unreasonable Behaviour.
Just so that your friend can understand a bit more of the reality, forgive me, for talking about myself, but I want to reassure her initial fears of living on the streets bit..given it's Christmas at all.
I too have a 'wonderful' husband who is claiming all the capital assets of the marriage were in fact loaned to me, and now he has left, I must pay him back! This floored me for months until, finally, he accepted this was a completely arse of an argument! He is now claiming 50% of the assets in my name, and has spent all the assets in his aside from the one's we have managed to get freezing orders on! He has repeatedly ordered me out of my home. I am still in it - he is not! So, your friend, if she can stand it, must remain in the marital home for now unless there is somewhere else she can go. However, I realise why this often is hell on earth as often times there's nowhere for the other person to go. And divorce can take many moons to resolve...
At the moment, he is paying me (hard fought for as it was) spousal maintanence (properly called Interim Periodical Payments). This you can get awarded very quickly (within weeks of your application going in, but only after you have started your petition to divorce) and it lasts until (at least) the court directs otherwise. The key issue is whether he can afford it! If he can't, she has no hope.
Obviously every marriage is unique, so every divorce outcome is similarly unique so it's impossible to say what she will leave with. The rule of thumb is: it will NOT be the case that she leaves with nothing at all - after all if the house has gone up in value, then half the value of that house increase minus capital gains, are hers.
Likewise, it doesn't matter if he was the earner and she the 'home-maker' she has still contributed fully to the marriage, so she's entitled to 50% of any accruals in pensions/other assets during this time (but not post-separation).
She is not entitled to half his income following the split.
That's why, for example, Heather Mills, left her similarly short marriage 16m pounds better off than when she arrived in it. The fact that there was a child involved obviously was a very important consideration. However, the rules are the same for us all.
I hope some of this helps. She won't get a bean for him being a cheating bastard though as 'fault' doesn't affect divorce law.