How much is the house worth, how much mortgage is there left on it? You should be looking at getting at least 50% of the equity in it if its a joint mortgage. Go see a solicitor, many will give you half hour for free. See where they think you stand.
You need to know what the value of the house now, in some areas it will have gone up and in others it won't. How much deposit was paid? Who paid the deposit? Were you married or not? You should still be due 50% of equity, but you need to know how much equity there is and then go from there.