Output VAT Error on Vehicle Sales

I have been preparing our monthly accounts and have discovered that one of our departments have sold a number of vehicles through an auction house and have completed the paperwork as qualifying for VAT. We have, therefore, suffered output tax on the sale proceeds when a number of the vehicles should have been margin with no VAT liability. The cost to us is just under £14k. I have contacted the auctioneers who inform me that all of the vehicles were sold to registered traders who would have reclaimed the VAT and they cannot now correct the paperwork. I’m guessing that HMRC will point out that the erroneous output tax cannot be corrected because there would be a loss to the Exchequer as a result. Do members know of any way to remedy the position?