Hi Clare. Thank you for your answer.
My ex wife has told me, though, that she is unable to release me from the mortgage until I have transferred the title to her sole name. I suppose my question should be "Is it possible to remortgage a property in a sole name while it is still registered in joint names, with the process of remortgaging including the transfer of title deeds"? Basically she wants me to transfer the title deeds before she applies for a mortgage, but I don't trust that she will. I think she is trying to trick me into signing over the property.