I suspect the safety advantage of 120V over 240V is probably mitigated with widely used GFCI/RCD devices. Also if the 240 was done split-phase style as in the USA, then touching a single conductor is no worse than what we have already. I would be happy if the default was a 3 prong outlet with line1/line2/ground. NEMA 6-15 outlets for say kitchen use (would be lovely to have powerful UK-style electric hot water kettles.) Maybe some new 10 amp version for regular living spaces (that still gives you 1920 watts with the recommended 80% maximum load)

But back to the original topic, we don't really waste that much power with wall-warts and such. Better to look at refrigerators, clothes/dish washing, HVAC.