Your post is very hard to understand.
Am I right:
The house was in joint names.
A settlement was achieved whereby the husband was to sign over his share of the house to the wife. She took on the mortgage?
Now wife wants to sell the house and buy another but the bank won't release the deeds because they want the husband to sign an authority to do so?
If not right, please post the correct information. Also in what form was this settlement- a deed of separation, a court order, a settlement made a court order or just an agreement, subject to deeds etc being executed.