"recently the action of switching off the wall switch has resulted in the house mains trip switch being activated"
I've been having some electrical problem relating to an outside light tripping the house circuit breakers even when its not on! (LONG story)
During my discussions of what it might be / might not be (cos both myself and the sparks are stumped) they explained that a house circuit breaker measures the "up" current and the "down" current and trips when theres a difference. This can also be caused by an old / worn switch. If one contact in the switch touches first then the circuit breaker will trip.
Try a different wall socket or replace the wall socket and see if thats helps...