Moving a Consumer Unit

It also seems to depend on the type of filament lamp. GLS types never take the breaker here when they blow. 'Spot' types, frequently. But not always.

GLS filament lamps typically have built in fuses to interrupt the resulting arc current that's often instigated by a break in the filament. This arc can keep growing as it consumes the remaining filament, replacing the resistive filament wire, now shrinking in length, with a negative impedance arc which rapidly increases the current until either the built in fuse(s) or else the lighting circuit fuse/MCB blows/trips on the consumer unit itself.

The 'Spot' types don't have enough space to incorporate such "anti-arc" protection so are more prone to blow/trip a lighting circuit fuse/MCB at the consumer unit.