PICD - Is the quotation issued in response to a PICD locked for changes?

A PICD for additional scope was issued to the Subcontractor and a response was received within the reply period. However, by the time the COntractor was ready to submit their response, the price of steel had increased substantially (£100/tonne). If the Contractor escalates the PICD to a CE, is the Subcontractor entitled to resubmit the quotation to recover the costs associated with the steel, or is the price locked as per the quotation first submitted in response to the PICD?