Sorry to read your post.
To answer ur question the bank will go for a judgement mortgage and seek possession. They sell at 175 and you are still on the line for 320-175 + their costs which can be 30k or more. I presume the house and debt are in joint names
If u hang around the judgement may include an attachment against your salary at source
the large excel spread sheet u refer to is the MARP process and if u enter into it and play ball it constrains the bank somewhat.
You mention conscience and I take it it is debt-rather than hubby related.
As this is a moderated forum I will say no more other than you need to look after your self, I take it there are no kids so I would, if you can, take the hastalavista baby option, after all its only money.
While you dont mention it, the divorce option does not give u the ducks anatomy style protection you need because there is a clause in the legislation that allows either party to come back to the well.
What I am hinting is at here is that after the 4 year living apart requirement, u get the big D and move on and away and then come back with a shed load of mula. Hubby can have another go at the divorce if he is on his uppers.
When the law came out first the clawback was optional, you could get a bullet proof big D but not any longer.
Keep well.