I agree with the comments above: there's no need to go mad, just calmly renegotiate the deal and remind them that there is a late-delivery penalty written into each new car order form. The dealer is required to write two dates on the form: a date after which the customer agrees to pay for and take possession of the vehicle and the latest date by which the dealer is required to provide the vehicle. Read the small print on the back of the UK order form, but normally this is an EU-wide directive.
