Upon bankruptcy your beneficial interest in the property is automatically transferred to the official receiver (or trustee in bankruptcy, as appropriate). If you're the sole owner of the property the title to the property will also be transferred to the receiver.
The receiver is then obliged to sell the property to pay off as much of your debt as possible. If it's in 'negative equity' the receiver will sell it and give the whole of the proceeds to your mortgage lender. (The remaining part of your debt to the lender is then added to all your other debts which the receiver will do his best to settle from your other assets).
http://www.insolvency...eleafletspdf/home.pdf
Chris