Which old box have you got? I don’t know about current policy, but in the past people who cancelled TV were sometimes left with the box just providing free to air channels, in the hope that they would re-subscribe in the future. However if the box failed or became obsolete, I do not believe that it would be repaired or replaced. You will need to connect a TV aerial or take out a new Virgin TV subscription, which would come with a replacement box of some sort, depending on what service you ordered. If it is a Tivo, V6 or 360 box, you should ask Virgin if they want it back, as all equipment remains their property, in theory they could ask you to return an older box, but I think that is unlikely.