NEC ECC: Responsible keyholder to provide access to correct Defects

School project which has been completed, in now due to close for half term. The E via the school have provided the C access to correct Defects since Completion and expects all to be completed before they return back after half term. The Defect Correction Period has lapsed but E mutually agreed to this extension.
Despite previous agreements, the C has since refused to be responsible for opening up and locking the site thus placing the burden on the E, citing insurance liabilities. Surely the risks are addressed by the C maintaining the CAR insurance policy under cl. 84? Therefore, can the C refuse to be responsible for maintaining the access provided to him and can the E be considered responsible?

The Contractor would be responsible to the extent that it is responsible for any insurance event under the liabilities clause. I.e. If they opened up and closed the Site correctly, bu the school got burgled on a Saturday night when no-one was there, the Contractor would have no liability.

So, in essence, what you say is correct with the above modifier.