If the whole place is wired in pyro, where would a sparky start.......by insulation testing the whole lot.
It could just be a single pot bringing the install down. The circuits would need to be split into smaller sections, by disconnecting at sockets, lights etc etc.
You could then pin-point the faulty area.
If it is pyro embedded in the wall, replacing or re-terminating a pot is going to be messy!
Imperial or metric makes little odds. There are charts which give conversions of the imperial to the most appropriate metric pot/gland. Even then, a spark should be able to strip a pot down and rebuild, assuming no one has tried before, and minced the lot!
If the install is old, it may well be time for a rewire. With no further info or photos, we couldn't tell you if this is the case.