If your home is in negative equity of around £8K and you alone are paying the full mortgage, not just your part (the mortgage provider does not care who pays the mortgage as long as it is paid) I doubt they will release your ex-wife from the mortgage document and therefore the liability of the debt. When/if the equity builds up if there are mortgage arrears the mortgage provider may try to obtain a repossession order and can apply back to the court for bailiffs to execute a warrant for possession of the house and sell it; it is unlikely they will do so whilst the market is depressed. Under English law any debt in your joint names is the responsibility of you both not just your part, the full amount of the debt. It is also possible for other creditors, in the appropriate conditions, to apply to the court for a charging order, against the property which would have the effect of turning an unsecured debt into a secured debt.
The above is the position under English law, you would need to explain the differences under Scottish law and the steps you say your ex-wife has taken to reduce her liability.