I've been looking at my options for going to France at the end of December and using my Tesco vouchers. I've found you can't use them with DFDS ferry, so the tunnel, checked this out and site says you can't book online and have to book on the phone and also the price may not be the same price as the online price. So do I have to ring to check what the price would be before changing Tesco vouchers. What do you folk do?