What happens if I move out, don't pay, and just hope for the best?
We do not recommend this. You might end up in a great deal of trouble:
The landlord could sue you for all money owed under the contract plus court costs. You could try to argue in court that the landlord is only due the amount of money s/he would have lost if s/he had made reasonable efforts to re-let your room (which might reduce what you owe), but arguing this might not help you if the landlord has actually been trying to find a new tenant.
Did anyone sign the contract to act as a guarantor for your rent? If they did, the landlord will try and extract the money from them; and the chances are that the guarantor will then come looking for you while not in the best of moods.
Whatever else happens, you will certainly never get any of your Housing Deposit back.
In short: "doing a runner" is usually a very bad idea and is certainly very risky.