In contract law, a contract consists of three parts. First, an offer. Second, acceptance. And third, consideration (aka payment).

Try formally DECLINING the offer in writing. Also, offer a COUNTER OFFER. The counter offer should be higher than the true value of the property, mirroring their low-ball offer. Alternatively, make the offer for your entire property (no portions).

Now, it is no longer a case where you are unwilling to sell, and that they must invoke some draconic law to force your acceptance. Now, it will be because of their unwillingness to pay.

Also, if there are any buildings that can be registered as historical buildings/property, no one can alter it.