I had a similar problem with a B&D rotary mower - model uncertain. I
replaced the switch with a standard 13 amp plug & socket combination clamped
to the mower. Worked OK until the rotary drive fell apart apart about 2
years later. Always used with residual circuit breaker as safety precaution.
Now replaced by a non B&D mower. I could not recommend anyone to buy a B&D
mower after my experiences - on mine, the handle kept coming loose from the
inadequate too short plastic lugs that were supposed to keep it attached to
the mower.

Bevan