[MovedGoalPosts]

If the bank has sent letters warning of non payment of the mortgage you need to act now to clarify the situation. Whilst banks don't take reposession lightly your credit ratings will already be affected, and if they do have to go down that route because nobody is dealing with the issue on your side, you won't be worrying about how to sell, you'll be worrying about whether you will one day have any money or an ability to put a roof over your head.

Ownership with joint mortgages is complex, and you will need to see a solicitor. Given the mortgage non payment confusion you need to do this pronto, even if it is costing you. The Citizens Advice Bureau may be able to point you in the right direction.

Realistically you will not be able to sell the property easily while there are issues with the mortgage as you'd need to get the mortgagor's consent. You'll also have problems unless all owners are agreeing to sell. Each party has a stake in the property, at least equal to their financial contribution.