think you'll find this covered under the "sale of uncollected goods act" long time since i done this at colege!! but goes something like this
think its six months before you can dispose of good and reasnobl step taken to inform or advertise that good will be disposed of if no response you can sell and keep costs to cover storage costs etc and give balance to owner
once its yours you can apply for a log book -dvla will then write the previous owner asking if car was tolen or any probs issuing a new log book then its yours