EOT entitlement for delay post handover

We have a situation were we are due to handover the project without stats in place which are clients risk. The Works will be complete mid September, it is then looking like we will keep possession of the site for a further 8 months until the incoming stats are installed and we will gain PC. If there are delays of the Contractors making which extend the Works from mid September onwards are they entitled to full prelim cost or will the CE be assessed based on reduced prelims required to keep the site ticking over from the date the works should have been finished to the date we actually receive PC.