Only skimmed through this thread, but this appears to be a property with little chance of equipment being used outdoors, was installed with full compliance to the regs at the time, and has not deteriorated to a dangerous extent since.
On that basis, the C2s should be C3s, and the installation is 'satisfactory'.
This is a case of a Morris Marina, fully roadworthy, and with a current MOT (actually, doesn't actually need one, IIRC). Perfectly legal to drive, but potentially dangerous nevertheless.
Anyone considering using it as daily transport would be well advised to find something a bit more compliant with current standards, just as the owner of this property should be, with regard to RCDs.
In short, the property is 'satisfactory' as far as the EICR is concerned, but the EICR should be accompanied by a note stating that it is actually unsatisfactory and strong consideration should be given to the recommended upgrade.