Beat you to it, I owe over 28k on mine!! Joking aside, a lot of repossessees have shortfalls the same size as yours, some bigger, some smaller.(posted 8189 days ago)Bankruptcy is a very big step to take, and should be considered very carefully. If the shortfall is your only major debt and you can handle the rest of your commitents without problem, then don't go for bankruptcy. You will lose your bank account and any other assets - savings, insurance policies etc for 3 years. It will be impossible for you to get credit, and even after you are discharged it will be hard, you will need to build it up again from scratch.
If the lender was to take you to court and get a judgement against you, then as far as I am aware, even after you are discharged from bankruptcy, then can claim on that judgement. But if they are given a pay out by the Receiver without getting a judgement, then that is it, they can get no more, Although I have read that where the bankrupt has a possible inheritance or other sum due in the future (even pensions), it is perfectly legal for the Receiver to come back and take the money, long after the bankrupt was discharged.
You can get more information from www.insolvency.co.uk and from any of the practitioners listed on their pages.
Read through the information on this website about shortfalls and how lenders are chasing repossessees. When and if you are chased for the shortfall, come back to the site and read up on what to do - remember the lender has to prove their claim including that they have sold the house at market value, so in reality your shortfall is probably nowhere near 26k.