Hello Jason,
It seems to me that the offer of of the "free" television was an inducement to encourage you to choose a particular make of van. As you were not offered the set for simply looking, but only on completion of the sale, it is irrevocably tied to the sale and forms part of the contract of sale. If the dealer has failed to supply the set, then that is breach of contract.
Talk to trading standards or hint that you make take it to the small claims court.
If that doesn't make the set materialise, then speak to a solicitor (or CAB)