The debtor or hirer may serve notice of cancellation of a cancellable agreement between his signing of the unexecuted agreement and—
the end of the fifth day following the day on which he received a copy under section 63(2) or a notice under section 64(1)(b), or
if (by virtue of regulations made under section 64(4)) section 64(1)(b) does not apply, the end of the fourteenth day following the day on which he signed the unexecuted agreement.