Hi, I'm a divorce lawyer and hope isheisn'the doesn't mind me pointing out that I advised her initially on Mumsnet!
In your circs, Sadmum, you will get more than half of the capital. This is because your earnings are much less than your dh's therefore your mortgage capacity is lower, and also because you have to house the children as well as yourself.
It may be better for you to stay in the house on the basis that when the children have grown up, you will sell and your dh will get some of the equity. This may be as much as half if he carries on paying the mortgage, but is much more likely to be significantly less.
If that's what eventually happens, clearly there has to be money in place to pay your outgoings and that will depend on how much you get by way of tax credits, how much you can earn and what spousal maintenance you get for yourself (dh will pay you 25% of his net income for child mtce in any event). You may also be eligible for housing benefit to cover the first £100k of interest on your mortgage, however h.b. doesn't kick in until about 9 months after you make your claim.
If you have to/want to sell the house, you should get somewhere between 60% and 100% of the equity depending on a lot of factors including how much you need to rehouse, his needs, your earning capacity, his actual earnings, the contributions each of you made (you're considered to have made an = contribution because you have children), length of marriage, etc etc.
You'll also get a share of his pension and poss. any other assets, eg savings, endowments etc but that depends how much you get out of the house.
You may be entitled to legal aid (now called Public Funding). To find out, go to the eligibility calculator on the Legal Services Commission website.
Then, find yourself a local family law solicitor on the Resolution website. If you don't qualify for legal aid, most lawyers will offer you a free half hour's advice. After you've taken advice from someone who has all the facts of your individual circs, then you can decide whether you want to go ahead and either divorce or negotiate a separation deed, on the basis that you'll leave divorce on the back burner for a couple of years.
Hope this helps.