I am not sure if you can recover the vat back on the purchase price of a car even if it is for business use. I seem to remember that when i bought a new Land Rover LWB County Station Wagon in 1988 that i was allowed to recover the vat because of the number of seats it had. If i had bought a SWB version with 7 seata i would not have been able to recover the vat. Also dont forget you have to be registered with Customs and Excise to be able to claim the vat back . When you eventually sell a vehicle that you have recovered the vat on you will have to pay back to Customs and Exise the vat content of the of the price you get for the vehicle.
You only get VAT back on cars purchased by a businss if you are leasing or hiring them, if they are for use in the course of your own business you are not allowed to get the VAT back.
If you are a trader, you can get the VAT paid on your stock back, but of course if you do so you must account for VAT when you sell the car.
At work we all run Nissan Terrano Vans as our company vehicles, but we have the seats left in the back. As far as C+E are concerned, if its registered on the V5 as an LCV you can get the VAT back. We also pay a much reduced amount of BIK tax on them over the "car" equivalent.
Reason I asked regarding the hammer prices is that I work in the Agricultural machinery game and any sales conducted in this area are all hammer price plus 17.5% VAT plus buyers premium (usually 10%.