Holy smokes, if you folks across the pond plug your stoves into 3kw, you indeed should never use that for cooking. The plug behind my stove can carry 12, about 10 continuous.
Now, about your issue with parallel cooking: you indeed can not send Max Power to two pots if they are on the same rail. However, even the cheapest ranges I've ever seen have 4 burners, two rails. Which means you _could_ boil two pots of water, as long as you use the correct two burners. You learn pretty quickly which burners share a rail. I'd imagine the really nice ones have a transformer per burner so it's never an issue.
And as long as you're not trying to send boil-in-20-seconds kind of power, you can use all the burners without noticing anything.
Now, about your issue with parallel cooking: you indeed can not send Max Power to two pots if they are on the same rail. However, even the cheapest ranges I've ever seen have 4 burners, two rails. Which means you _could_ boil two pots of water, as long as you use the correct two burners. You learn pretty quickly which burners share a rail. I'd imagine the really nice ones have a transformer per burner so it's never an issue.
And as long as you're not trying to send boil-in-20-seconds kind of power, you can use all the burners without noticing anything.