$6000 seems like a lot of money. Did you ask the CH Sales person to void it if you are prepared to sign on the spot with your pen in hand or were you just 'shopping'. I was in the same situation but 10 months instead of 12 months. They wanted to charge $500 per month for delay (12x$500=$6000).. but I got CH sales to void it when I was prepared to sign.. he has to phone up the sales manager for approval. Alternatively, maybe ask for upgrade credit for the sum.
Just to give every one an update, we asked for a discount or upgrade credit and carlisle refused, reason being was they are locking the price for 12 months. Considering their promotion was ending soon and the house price might go up, we signed up anyway. Thank you every one for your help