Hi there, so sorry you are going through a difficult time. You can not force a sale through but it could be done through court. You would need to go and speak to a solicitor. A judge could rule that the property should be sold. Especially if there are arrears on the mortgage.
The mortgage company will only allow you to take on the mortgage if your income is enough to cover it. It used to be 3.5 x salary when I was in the mortgage business but I know that there have been lots of changes in the last 2 years.
The best way would be for both parties to agree to a sale. If you have arrears this would be damaging to your credit rating and the bank can start repossession proceedings which is not a good road to go down.
I really hope you can sort things, CAB can help but I would go and see a solicitor.