Can I terminate the contract I have with a supplier who has not supplied what they said they would?

At law, the right to terminate a contract for breach arises if there is a substantial failure to perform.

Any defect in performance must attain a certain minimum degree of seriousness to entitle the injured party to terminate.

A failure in performance is substantial when it deprives the party of what they bargained for or when it goes to the root of the contract.

For less serious breaches, a right to damages may arise, but not a right to terminate.