seem to remember the DNO can refuse to supply a dangerous install.
if you stand by your eicr ( and crumbly lead sound about as bad as it gets) ring the dno and ask for an intervention.
that should get the clients attention eh? no power and big dont use label.
had similar couple years back.
tested 6 bed, 3 floor victorian house. passed (just) but told owner (read 'slum landlord') no additions or alterations and get a rewire.
also put down 3 monthly retest. yes, 3 monthly.
couple months later, local council rang. he'd put in for house of multiple occupancy. saying I had said place was ok.
Told the council no way, forwarded copy of my certificate.
found out he'd been shut down by council and fined and now got council on his back big time.
so try the council and the dno.
worth a couple of phone calls and might just bugger the architect up a bit.