As stated above first you need an order that the debt is to be repaid and then if payment wasn' forthcoming you would need to apply to enforce the order. One option is to apply yourself for a Charging Order, then apply to the court for an Order for Sale. If granted then the procedure works just as if the property was being repossessed - the house will be sold and the creditor gets his money.
However, there's no guarantee that the court will grant an immediate Order for Sale - occasionally the judge may think that, as the loan is secured against the property, the creditor can simply wait for his money, especially if the debtor is in a position to pay the money back in installments.