Have you asked for a copy of the mortgage application form, this should show what income information you both gave the bank at the time. I am presuming the mortgage is in joint names so you were involved in the application, what income information did you provide the the bank, you must have expected to be able to pay it back from something, why else would you have taken a loan until that age?
The Ulster Bank case was the opposite to yours in case I didn't explain correctly, the customer was declined a loan based on being too old and won a discrimination case.