Ford Focus - Taxing a car bought at auction - hatman

If buying a car at a large car auction privately, is it possible to obtain the full V5 or the green slip when purchased so that the car can be taxed for the drive home? Or does the auction send off the complete V5 to the DVLA? If they do, how will it be possible to tax the car to drive it home as most cars at auction don't seem to be taxed.