Can I sue my buyer/seller if they pull out of the Conveyancing transaction?

No. If exchange of contracts has not taken place then unfortunately there is nothing you can do if the other party pulls out of the transaction.   The only exception to this if you have entered into some sort of lockout agreement.   Once contracts have been exchanged then on the basis that the other party withdraws in such a way that they breach the contract (in other words the contract does not give the right to the other party to withdraw), then you should be able to pursue the defaulting party through the Courts for breach of contract.   Most Conveyancing contracts have clauses specifically dealing with the penalties for breaching the contract.