I am familiar with the NEC (although not a professional in the area) and know that drussell's points are sound. A grandfathered electrical installation does not make you liable if there are no explicit problems with it - something quite unusual to happen, given that 100 year-old houses are almost guaranteed to have had major renovations at a certain point in their lifetime.
Regarding the problem at hand; I have lived most of my life in an apartment building without ground (the feeder was a three-phase 380/220) and the rare occasions I was shocked by an appliance it was entirely its fault (also by my electronic experiences, but that was entirely my fault
) - therefore, it is not a "death trap" or anything of the sorts if it is well maintained.
As for grounding your house on the feeder installation: you can't guarantee it won't be disconnected at a sudden if the maintenance crews need to work on it (not to mention it may be illegal, but I don't know the details). Also, as others have mentioned, you are connecting your ground to a system much more exposed to HV faults or electric discharges, which can raise the voltages to dangerous levels. I have seen this happen and obliterate electronic equipments (Audio equipment, TVs, VCRs...) in entire neighbourhoods - usually other appliances (fans, lamps, blenders, etc.) are much more resilient to these.
As for fuses and circuit breakers: they are usually dimensioned to protect the wiring against overheat, not the person or the appliance.
Every plug is fused in the UK, whether it has an Earth or not.
Yeah, that's because you folks use the strange-to-us method of essentially stiffly connecting the whole house directly to the mains feeders and letting the plugs try to play mediator.
Your system seems insane to us, and our system seems insane to you, but they both work.
I don't quite get that: do you mean that in UK there is no main circuit breaker box?