MTA (Motor Traders Assoc) might be able to help, but i doubt it.
I'd be trying to get a slightly firmer date, then a few days before it arrives, just lob in and cancel the sale, get your refund. If you have your heart set on the Bitsoshiti either go to another deal, screw em for a bargain bagging out whichever dealer has done this to you. OR you could just go back a few days after you cancel and do a new deal with a few extras.
Good luck with it