Or do as I did,
Not pleasant but needs must,,
similar circumstances, I was paying the mortgage, wanted to sell but my ex-wife wasn`t having it as long as I was paying she saw the equity rising without any contributions on her behalf, so I did the only thing possible to force her to agree to the sale.
I stopped paying the mortgage and after 2 months the RED letters were getting serious about repossession so I presented them to her and explained that if we didn`t sell and split the equity then it would be repossessed and sold at a loss and she would be joint liable for any difference.
After some expletive language she agreed and the house was sold and we have both moved on with some money and a clear credit history.
It was tough but had to be done,,,,, and no regrets.