I bought a van but have no V5, can I sell it?

I bought a new van from a local dealer in March. I am now looking to sell the van, but the dealer hasn't given me the V5. After some investigation the van I bought was a pre reg but this wasn't explained...

What's the best way to sell a van quickly?

We'd like to sell two of our vans. What's the best way to do so quickly?