Ask an Property Solicitor. Get an Answer ASAP.
Thank you for your question
My name is Clare
I shall do my best to help you but i need some further information first
How old are the children and were your wife and her ex married at all?
Are there actually arrears on the mortgage account?
How much is the house worth and how much is outstanding on the mortgage?
Can you not get a mortgage in your name?
What work do you actually wish to do on the property - does it need planning permission?
You can simply go ahead and do the work - if he seriously wishes to stop you then he would have to make an applictaion to the court for an Order preventing the work - which is unlikely to be granted
The only point to remember is that he will benefit from any increase in value and it may be difficult to claim any extra equity to reflect that
Please ask if you need further details
You are most welcome I hope all goes well