This is taken from the T&C's on my order last year from Kings Lynn Audi:
"9. If the goods to be supplied by the Seller are new, the following provisions shall have effect:
d. If after the date of this order and before delivery of the goods to the Purchaser the Manufacturer's or Concessionaire's recommended price for any of the goods shall be altered. the Seller shall give notice of any such alteration to the Purchasers and
i. in the event of the Manufacturer's or Concessionaire's recommended price for the goods being increased the amount of such increase which the Seller intends to pass to the Purchaser shall be notified to the Purchaser. The Purchaser shall have the right to cancel the contract within 14 days of the receipt of such notice. If the Purchaser does not give such notice as aforesaid the increase in price shall be added to and become part of the contract price;"
So it appears you have 14 days to cancel after they tell you about the increase.
If you don't you are accepting to pay the increase.
The order is assigned to a build slot by a sales administrator within your dealership. They are 'given' a certain number by the factory and they choose which orders to put where (based on what model the slot is for). My dealerships sales admin had a BW assigned within hours of me paying a deposit. There's no good reason for them not to have done the same with yours.