I am in the process of purchasing a new build and was due to receive a stamp duty financial incentive from the builder in exchange for doing my carpets myself. Now that the holiday has been extended, the homebuilder has refused to change the terms and are saying that it's null and void now that there is an extension even though this wasn't pre-stated in the terms. Now, they want to send out riders to change their terms. Should I fight it or just leave it and continue with the old plan of doing my carpets?