I know you might be feeling emotional about this, but you need to put emotions aside and think pragmatically.
If you actually want to go ahead and have the child, you need to arrange the finace to bring the child up. Letting his wife know that she is married to a jerk won't solve your issues.
His father has a legal obligation to support the kid, regardless of whether he is married or not, to you or to somebody else, etc. You will have to go to court for this. Normally, the court does not deal with child support payments in divorce and instead Child Support Agency does, but this is not the same here. Besides, CSA used to deal with case where income was something like below £100k p.a. (I might be wrong about the precise number). With incomes above that, it was court's domain.
You need to find a good lawyer now. I don't know what your income is and if you can afford it, but it will be money well spent. (good family lawyers rarely charge below £300/hr in London). You might even qualify for legal aid (not all lawyers work with legal aid, but many do, even top notch ones). Go to Chambers and Partners and see their guide on family firms to pick one.
http://www.chambersandpartners.com/UK/Editorial/39098
Good luck! And as I said, try to stay pragmatic.