Check if you own it as joint tenants or tenants in common, your solicitor should be able to confirm and you're likely to have specified this on your puchase.
If joint tenants if one of you dies the survivor gets the house, if tenants in common it goes in accordance with your will (depending on liabilities, debts etc...) or intestacy rules if no will (probably your parents if you have no kids).
It's always a good idea to have a will in any event, get it drawn up properly, stored safely (ie with a solicitor) and traceable so it's findable when you die and review it and change if necessary on any important events such as having children or financial gains and anything else significant.
If you marry it becomes invalid (think this is still the case)! You would need to draw another one up.