The PC still legally exisits until the Administrator has wound it up and thus in theory you have a right to pursue the Administrator and I would certainly look seriously at this route. The administrator is the director of the company and is not exempt from any duty under H&S legislation. It is time a test case was taken out on this and one would hope that the HSE might see it as important enough to pursue.
This is not an unusual situation as there are many key documents and certifications/guarantees for the file that are produced in the last few months or weeks of a project. Some may be in the PCs cabins/offices and it ought to be the responsibility of the administrator to sort these out.
Bob