WBAC is a safe, secure place to sell.
They are owned by BCA, British Car Auctions which is in turned owned by a large Private Equity Company,
Safe, BUT I've heard from a reliable trade source that they will 'chip' you on price when you turn up for handover by finding tiny things you couldn't declare (because of how the online menus are set up), they know you've turned up committed and want the cash
