Well, I make no effort to use one item at a time, and happily have both ovens, two hobs, the kettle and the washer and dryer going when I need too, but do make an effort to use the washer/dryer/dishwasher ect at night.
The only modification I'd make would be to put my own circuit breakers in, set to trip at 3.95kw, 3.96kw, 3.97kw, each killing sequentialy unimportant loads and a final one to kill everything but lights at 3.98kw

Calling out an "engineer" because the fridge and freezer both clicked on whilst you were boiling the kettle and making toast seems of questionable green benefit.