Accident caused by third party but left paying hire purchase shortfall

I had an accident last year on a dual carriageway.  The driver of the other vehicle drove into the back of my car at high speed.  Both cars were written off.  Initially the third paties insurance company excepted liability then took that back, as a result this has delayed everything.  I had initially asked for the car back as I was told my car was a category (d) write off.  My insurance company told me that there was no point in them repairing the car as the repairs may exceed Â?4000 and if that is the case they write the car off.  My Engineer was meant to ring me back in regards to getting the car back.  I had rung my insurance company on several occassions asking what has happened with the claim and whats happening with my car and got nothing, everyone kept telling me different things or just didn't know what was going on and assured me my engineer would call me and let me know.  I also did not sign and send back the letter giving authority to dispose of my car as I clearly made a point to say I wanted the car back.

Anyways they finally paid the 'estimated' worth of the car to the financial agreement company.  There was a shortfall of Â?2500 which I am having to pay back.  Is there anyway of claiming this money through compensation?  I would not being having to pay such a large some money if it wasn't for the accident which wasn't my fault.  I have also looked into the gap insurance, but unfortunately my financial agreement company does not offer this, so I am having to pay the shortfall in full. 

Also I found out several months later that my car had been sold to a scrappage yard, only because the dvla wrote me saying someone has requested to be named as the registered driver of my vehicle.  I called my insurance company and the first person i spoke to did not even know the car has been sold and could give me no information.  It was only after i demanded to speak to her manager that she forwarded the call on to someone who told me the car has been sold in december (bear in mind i found out only in june).  He apologised profusely and told me this was not their policy as they could not do anything without the letter of consent.  I asked what now and he just said they could not do anything and just apologised.

I am also being chased by the dvla for failiure to tell them I had sold the car on, for not paying my roadtax and for failiure to inform them that my car had been crushed.

I am being tormented by the actions of another person.

What can I do now?