How long ago did this all happen? - for the bill to rise by 2000 pounds, i would have thought that you may have left it some time? After you stopped paying, were you still using the car? How long between black horse saying they would take the car back and you ringing them to arrange it and be told they also wanted the money?
I am asking this because if they said they would take the car back (a bit strange since they are a finance company?) and then you didnt get them to take it back immediately that is very different from them saying they will take it back then you waiting 2 years to contact them