Gary,(posted 8510 days ago)You say you have seen 'all the information' about the property, but this appears to comprise just one valuation report.
You are entitled to put Abbey to 'strict proof' before you even consider making any settlement, and you should ask to see the documents on which Abbey's claim is based. These include the mortgage deed and conditions and the MIG policy. You might also ask to see the money judgement (if Abbey has one). The reasons why are detailed on this site under 'Repossession', and you *must* read this section.
If Abbey refuse you sight of these documents then you should ask yourself why. (Again, see under 'Repossession'.)
By the way, you are probably six years from the point at which you defaulted on the mortgage leading to repossession, or from the repossession itself (or soon will be). This is why you need to see your mortgage deed, to see whether Abbey really is entitled to go after you after six years. Again, there's more on this HRP site about all this.
As for the valuation: Why was there just one valuation? Was it fair? Did it judge the property as a repo or as a 'normal' house (ie was the valuer aware that the property was a repo - I'll guess that s/he was well aware and underpriced it accordingly.) Did the valuer have any connection with Abbey or estate agents linked to Abbey? Was the property actually marketed properly?
Did you receive the proper, full statutory instruments of notification, and were these sent on time and to the correct address? (Again, see this site under 'Repossession'.)
Until you see the evidence that you do actually owe the money Abbey claims you owe, in my opinion (and I must stress that this *is* just my amateur opinion) the ball is in Abbey's court. If it were me I wouldn't admit any liability, make any offers of settlement, and I certainly wouldn't fill out an Income and Expenditure form.
I know it's a stressful situation, but, in my opinion, it's possible that this may be what some lenders and their firms of debt-collecting lawyers depend upon to get vulnerable people to cough up on unproven 'debts'.
You have got to learn to live with this. Read this site from top to bottom. Ask for support via this Q&A board when you need it.
And good luck.