When can revised quotations be submitted for the same Compensation Event under an NEC 3 contract?

The contract provides that the PM may request the Contractor to submit a revised quotation but does the absence of such a request prevent the Contractor from submitting a revised quotation in circumstances where the PM has neither Accepted the original quotation or made his own assessment? Is the answer different depending upon whether or not the Contractor has implemented work relating to the original quotation?