I purchased my 1st van whilst it was still on lease,and the seller had the relevant paperwork from the finance company stating that he had permission to sell the vehicle,I also phoned them to confirm that he was able to sell it.
When I paid for it the cheque was made out to the finance company and not to the seller,they also issued a statement saying that I had full ownership and that they had no further interest in the van.
So he got to clear the lease and I got a van at a bargain price.
There may be other options and I am sure someone can advise you.-John